Hello student if you fall in SEBC category now and have enough documents to claim your category then yes you're eligible to appear in SEBC category in NEET PG even if you've pursued MBBS in OBC category.

Eligibility - Candidates must have passed MBBS degree from a recognized university and need to complete one year internship on or before 31st March 2021.

For more details refer to the link mentioned below - https://www.google.com/amp/s/medicine.careers360.com/articles/neet-pg-eligibility-criteria/amp

Feel free to comment if you've any doubt.

Good luck