What should I do about muscle indent in left upper buttock? Muscle atrophy.

Thank you for your question.  Photos would be helpful to answer your question more accurately.  It sounds as if fat injections may be the better option for you. Best of luck,

I can much better address your concerns if you could please first send some photos of the area of interest. Glad to help. 

I agree that the indentation is likely associated with your shots.  I have been very pleased with Sculptra as a way to fill out buttock indentations. I find that the procedure requires little to no downtime and is office based. I have done minor dimples to full buttock augmentations, albeit the latter is for people who want a modest augmentation and with little fat to donate. At times, if the indentation is associated with a scar, then subcision or a scar release may also be warranted. 

Hello dear!!
Thanks for the question and provided information as well.
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 :)

This actually sound more like a fibrosis do to trauma than an atrophy. Please send some pictures and one with your leg flexed so we can evaluate more your case and suggest you a treatment.Find a Board Certified Plastic Surgeon and discuss what will be the proper treatment to achieve the result you desires.Regards,Dr. Luis Redondo