1) nominee is a trustee for all legal heirs .
2) since your uncle had made a nomination of the flat in your name society is bound to transfer flat in your name on death of your uncle .
3) at most society can insist you furnish an indemnity bond in favour of the society .
4) if society refuses to accept your application for transfer and Registrar refuses to take any action file an RTI application with the registrar as to what action has been taken on your complaint .
5) ultimately you may have to move cooperative court for necessary reliefs