I got a steroid injection on my buttock & 2 months later it formed a dent and skin seems thin and discolored. What should I do?

Hello dear!!
Thanks for the question and provided information as well.
Based on your description, it looks like you could benefit from fat transfer procedure to fix your problem, but unfortunately, without pictures, it is very difficult to give you a proper answer. 
l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

An exam or pictures would help to make a determination.  Sometimes fat transfer is very useful to improve these areas.Kenneth Hughes, MDLos Angeles, CA