Unauthorized Parking

Dear Sir/Mam, Namasthae! We have purchased an apartment in Bangalore city within BBMP limits and were peacefully enjoying our living since last 1.5 years. We have purchased the property from a House Building Socitey. Now the issue is, our co-occupant in the building is repeatedly creating nuisance by parking his car in our parking lot/ parking lot allotted to us by the builder/housing society. The problem is he was fine until the day we moved abroad,the very next day we boarded on to our flight,he has parked his car in our parking lot and arguing with our parents, who have just moved in to the city and helpless regarding this issue. He repeatedly hesitates stating that, he has purchased first in the apartment building and he has to enjoy parking space which is convenient to him on first come first serve basis [ Please note he was quite until we were there ]. Housing Society has marked Parking Spaces in our apartments with flat numbers mentioned and they have mentioned in the sale deed that, Occupants have to park their cars in the ALLOTTED PARKING LOT ONLY. Other than this clause, there is nothing mentioned. In this case, he is now parking his car in our allotted parking lot and creating nuisance stating that, he couldn't remove his car since its convinient to him. Our Hosuing Socitey, who alloted its unit to us, also warned him not to disturb us in this regard. Still, he doesn't seem to listen to this. Kindly help what should i do?