Can builder assign common area despite my registered undivided share?

I bought a builder floor (Stilt + 3) in Gurgaon. As per our understanding, each owner gets one parking lane, and the remaining lane with the lift and common room is shared. I’m the first to register, and my sale deed clearly mentions a 1/3rd undivided share in the stilt parking floor. No other registries have been done yet. Now, the builder has sold another floor and, without my knowledge, assigned the common room on the stilt to the new buyer, claiming that OC approval gives him the right. Can the builder legally do this when I already hold an undivided share in the stilt? Does the OC override the rights in my registered deed? What legal steps can I take to stop or challenge this? Any help is appreciated.