Conditional sale deed

Hi, I have a situation regarding a property. My deceased mother bought a site from housing society in Bangalore in 1987 with a conditional sale deed that the site should not be sold within a certain number of years (not sure if you call it a lease)? My mother however passed away in 1998 and the property is now come into my name as I'm the legal heir. A week ago I received a call from a staff of the housing society enquiring for my deceased mother and the property. On further conversation he mentioned that I cannot sell the property now even if I wish to as it was not legally mine still due to the conditional sale deed. So he is demanding a sum of 1 crore to register that property into my name and that amount is calculated from 1997-2015. When I met him personally face to face he is speaking another story of just giving a sum of 23 lakes and make it a absolute sale deed into my name. I'm confused over this matter and I need some legal advice on this matter please. My email is