Owner not returning complete deposit amount

Hi, I rented a flat in Pune PCMC region in November 2017 and the agreement was done, I paid 60000 as a deposit, I lived in the same flat till 27th May 2021. The rent agreement was renewed only in 2018 and then the owner decided to sell the flat so we both agreed to not renew the agreement. Now owner has deducted 15000 from my deposit for Society Maintenance and flat repair charges, whereas in agreement it was clearly mentioned that Licensor will pay any Maintenance and Taxes. This is mentioned in the Agreement for both years. Maintenance Charges: That the all outgoings including all rates, taxes, levies, assessment, maintenance charges, non occupancy charges, etc. in respect of the said premises shall be paid by the Licensor. Flat was owned by their Son who lives in US, his parents were managing his property here. now they have sold the flat. i have never paid the Society Maintenance in my 3.5 years of stay, for the times that i paid the Maintenance, always deducted the amount from my monthly rent and they never complained but now they are saying the maintenance had to paid by me. i have 2 questions now. 1. what can i do to make them return my money. 2. is it worth to take legal action for 15000 Rs? thanks.