Has the dispute with the builder been resolved? Had your mother and grandmother been admitted as members before their deaths? If they had not been admitted as members, they would not have been able to make any nomination. Had they made any Will? Are you the only natural heir of your grandmother and your mother?
You have not stated anything about your dispute with the Builder. Unless and until you have been admitted as a member of the Society, the Society is within its rights to refuse you permission to park your car.
If the dispute with the Builder is still unresolved, you can go to the Consumer Court. In another case against a Co-operative Housing Society, which is similar to yours, the Maharashtra State Consumer Commission has given judgment in favour of the prospective member.