Harrasment

I sold a FILM Roll SLR camera to a guy in FB..He bought it for 7000 Rupees.Then after 2 weeks he is calling me and telling that he doesn't want the camera as he is not getting film rolls.i told him it is available in amazon and flipkart but he told he doesnt want it and wants his money back.I am a Dialysis patient and i spent it on my treatment.I blocked his calls but he called from his friends phone number started using bad words when i am on Dialysis.Since i am a Kidney failured patient i cant handle when some1 scolds me .My heart starts beating rapidly!..He told me he will give my number to Police if i dont give him the money.I did not cheat in any way.I gave him the camera he gave me the money.There is also no proof that i only gave him.He is scolding me and told he will beat me when he sees me again..This happened in August.Now its december and he stills msgs me bad words.Should i msg him back and scold him bad words or just leave it?.Dont care whatever he sends and do my own work.No one in my family knows this.Also i did not cheat him anyway.Since i am a dialysis patient if i am thinking if i msg him back or call him then this will become a big matter..What should i do please tell me.