Admission to AIIMS will be conducted at All India Counselling. So under OBC Category for AIIMS, your score should be nothing less than 625-650. This is because at All India level, the cut offs are usually higher. And coming to AP, it depends on the area you are a locale to i.e AU, OU and SVU. Now in 2018, the cut offs for BC Category under various areas have been as follows:

AU: 484

SVU:473

OU: 458

Now this is 2018 data and cut offs change every year depending on various factors such as no.of Candidates appearing for the exam, no.of Candidates qualified, top NEET score and difficulty of the exam. For 2020, your target should be nothing less than 550 for a seat in a GMC in AP. For guidance in counselling and admission, we have MBBS Companion:

https://www.careers360.com/mbbs-companion