You cannot make any changes to your NEET application. But when you register for either All India Counselling or State Counselling, please enter the correct information. Your 12th marks are only used to assess your NEET eligibility and not for admission to Medical College and so you can be fine. But this doesn't mean that entering wrong information and not correcting is allowed. But as it has already happened and you do not have a chance to correct it, what you can do is during document verification. please do not forget to take the original documents. That way you can avoid any issues during counselling and admission. . For any guidance during counselling and admission, you can use our MBBS Companion: https://www.careers360.com/mbbs-companion