How can I fix a very noticeable cortisone injection indent? (Photos)

This scar can be improved with laser spot treatment, fillers, microneedling/prp and subcision to help texture and blending. I recommend getting a formal evaluation with a scarring expert. Best, Dr. Emer

This is unfortunately a common problem even though it should not be.  The best treatment is to have some type of filler injected .  It might take two or three sessions to get total correction and then annual maintenance treatments might be needed

I find that micro fat grafting works best in these situations It can also be combined with PRP(platelet rich plasma)

The best option for restoring this defect is fat grafting. This can be performed simply under local anaesthetic. The cortisone has essentially caused resrption of the underlying tissue and fat, so replacing like with like tissue, i.e. fat would be preferable to using temporary fillers.

I recommend HA filler injection (temporary), fat grafting with syringe lipo of 50 cc's, Sculptra injection/s, or both options in combination (best). Fees in $1,000 to $2,000 ranges. Seek in person opinions from boarded PSs in your area. 

This can easily happen after cortisone injections.  Cortisone decreases the inflammatory response so the area can heal, but it can also cause collagen breakdown.  The problem is, inflammation itself can cause collagen breakdown so it is hard to say which is the culprit.  The scar may have been even bigger without the cortisone, or the cortisone caused it to be bigger then it would have been.  There is no way of knowing for sure so don't be too hard on your injector.
The good news is that early on in the process dermal filler can be extremely helpful.  You literally fill the area out with hyaluronic acid, or other fillers, before the scar matures and it helps the area remodel with a better cosmetic outcome.  In general it takes 6 or more months for the scar to mature, but the earlier you get filler in there the better.
Hope this is helpful. 
Dr. Amy