Hii Ankita 

Since ,you have secured 12648 rank in sc category .It might not be possible to get admission in AIIMS New Delhi ,but yes you can easily apply for other AIIMS.Go through the last year's cutoff given below For AIIMS in sccategory ,given below-

1)AIIMS patna- 14195

2)AIIMS Raipur-13607

3)AIIMS Nagpur-13638

4)AIIMS Guntur-14510

you have also slight chances of getting a medical seat in AIIMS bhopal, rishikesh or jodhpur ,if we consider 2017 cutoff.

i hope this information proves helpful to you

All The Best