Farha, it is not clear if you want to know about AIIMS MBBS or AIIMS PG. Because AIIMS MBBS exam has been scrapped and now admission to all of 15 branches of AIIMS will happen through NEET score through All India Counselling conducted by the DGHS. So if your question is if you can study MBBS in AIIMS after studying BHMS, yes you can. Because NEET has no upper age limit. If you have had 50% aggregate in your 12th in Physics, Chemistry and Biology, then you are eligible for NEET. It is 50% for General Category, 45% for PWD and 40% for OBC,SC,ST.

Now if you are enquiring about AIIMS PG, then with BHMS degree you cannot appear for AIIMS PG because this exam is for MBBS graduates for admission to MD/MS courses in Medicine.

Follow the link for all the eligibility criteria for AIIMS exam and clear your other doubts too

https://medicine.careers360.com/articles/aiims-mbbs-eligibility-criteria