originally you were tenant of premises which was owned by landlord
then you paid certain sum to landlord and in consideration landlord transferred his reversionary rights to you such that you became absolute owner of premises
if there is a transfer of any rights pertaining to immovable property for a sum exceeding Rs.100/- then the document recording such transfer is liable to be stamped and registered which gives a clear title to the transferee
in your case that is not done
however society of all such tenants (later converted to owners) is formed and that society has recognised you as its member and I assume you also must be having a share certificate attached to the premises
you also have the possession and also must be paying all outgoings and all utility bills must be standing in your name
therefore from the point of view of future redevelopment, you are sorted
however if you proceed to take a bank loan against mortgage of this property, then bank may not sanction your loan in absence of a proper registered document
also if you sell this property then on the sale deed between you and your buyer, additional stamp duty with penalty may have to be paid which was not paid on the earlier document between you and landlord.