This is clear case of deficiency in service. Issue a lawyer's notice  seeking refund of price with interest, expenses towards medical expenses. After that file a complaint with all medical record in District Consumer Forum  under new Consumer Protection Act, 2019 under which  proceeding are very fast. You will get refund with interest, compensation for mental harassment, cost of complaint, medical expenses and lawyer’s fee. It is common knowledge that symptoms of virus will be visible immediately. There is incubation period. That fact can be established. On that count, you need not worry.  

Issue breeder legal notice to refund your money 

if he refuses file complaint against breeder before consumer forum and seek orders to direct breeder to refund your money 

also seek litigation costs and compensation for mental torture undergone by you 

Act as mentioned herein above 

rely upon vet report that such young pups are not to be sold and that pup had medical problems prior to sale 

Hello, 

1. You must issue a legal notice to the breeder demanding refund and compensation including expenses incurred for treatment of the pup. 
2. If he doesn't comply you can take him to consumer forum and lodge complaint with the police for defrauding. 

- You should send a legal notice for claiming refund of the amount 

- Further , if no response then file a compliant before the Consumer forum against the seller and claim compensation as well for the said mental agony. 

- Further you can get also refund the medical expenses after submitting the proofs before the forum. 

Dear sir,

1. since it is a deficiency in service on part of the breeder, you can issue a legal notice  seeking refund and medical expenses and costs for mental harassment

2.if he  refuses you can file a complaint before police for fraud and also file a case before the consumer court.

Thank you

1. You must move the consumer court on grounds of deficiency of service and unfair trade practice against the breeder. 
2. I'm willing to offer my services as your counsel (advocate).  However, to be of any assistance to you, I need an exhaustive consultation session with you first. You need to visit me for that. 
3. I'm based in Mumbai /NaviMumbai just as you are...  Hence, it should be much difficult for you to visit me for exhaustive consultation. 
4. ९८२०८९७८८४. (Nine eight two zero eight nine seven eight eight four) 

The seller cannot accept the liability after having sold the puppy, you should have examined the puppy properly before taking delivery.

Do you have a medical certificate duly certified by a vet doctor about the health condition of the pup you desired to buy?

If not, since you were in a hurry to buy the pup you did not take interest to obtain such certificate including the other relevant certificates from the  breeder at the time of purchasing, which amounts to your negligence.

Most dog buyers don’t realize that finding the right puppy for your home is fraught with pitfalls.

It is not as simple as walking into a pet store and walking out with a cute puppy.

You should not have bought  your puppy without an exhaustive “background check.”

An unscrupulous breeder is only after profit.

He does not care about his dogs’ welfare, nor does he care about his litter’s health or temperament.

Buying from a bad breeder will result in a challenging dog ownership experience.

Your puppy could be sick, have an aggressive temperament, and other health issues that might show up even as it grows.

If your breeder is a registered or a licensed seller and if the puppy's parents are kennel registered, you may first issue a legal notice tot eh breeder about this and inform him that he cheated you by selling a  sick puppy due to which you suffered not only financially but also physically by running around vet doctor every day.

You can demand return of your money by taking back the sick puppy as a compromise or you would be constrained to sue him in a proper forum as per law.  

You should have asked the breeder about the veterinary history of his dogs.

Dog breeds like the German Shepherd, Pug, and Husky are prone to several health issues such as hip dysplasia.

If you had planned on getting a dog breed, you should have learned about its health.

You should have talked to the  breeder about his dog’s medical history.

Good breeders will have in-depth knowledge about their dog’s health and will be able to give you useful tips about their breed.

Most good breeders will be finicky about people handling their puppies.

Since puppies can contract diseases, good breeders don’t allow buyers to handle their puppies.

Good breeders match puppies to buyers. Most breeders will not show a buyer the entire litter.

They make the match based on the buyer’s experience and the puppy’s temperament.

Responsible breeders will not negotiate the price.

Also, expect to pay a premium for his puppies.

It appears you have not taken care of the most essential things while buying the puppy neither the breeder seems to be a genuine person.

Basically the puppy less than 60 days should not be bought.

You may consult a local advocate and issue a legal notice and decide further course of action based on his reply.