My landlord entered my flat without permission and changed the lock — what are my rights?

I live in a rented apartment in Pune. My landlord showed up while I was at work and changed the locks without informing me. He claimed it was due to maintenance issues, but he didn’t give any prior notice. I’ve been paying rent on time and the tenancy agreement doesn’t mention such actions. I’m stressed as he refused to give me the new key until I pay an extra ₹10,000 which wasn’t discussed before. What should I do legally to access my flat and ensure this doesn’t happen again?