Hello Aman,
Students who belong to reserved categories are required to submit the certificate at the time of admission to the college. If you have filled your category as OBC-NCL then you will have to submit the certificate also to avail reservation.
If you are unable to submit the OBC-NCL certificate then the college might cancel your admission or in that case may be you will have to apply for admission under General category.
Every college has its own criteria. So, you should contact the concerned authorities of the college.
Good Luck!