I have a large dent in the top of my thigh. What can I do to repair this area? (photos)

A hematoma from previous trauma could cause this type of deformity.  A steroid shot that wasn't deep enough could as well.Fat grafting would be a nice option for you.  It will probably take a few sessions to achieve a complete result.  Good luck.

Hematomas/bruising are well known to cause subcutaneous fat atrophy. It should only be treated by fat to replace what is lost. The only debate is whether this should be done by fat injections or a dermal-fat graft. There are arguments to be had with either approach as its relatively small size makes its successful correction amenable to either approach. I would recommend an initial fat injection treatment with the understanding that a second procedure is highly likely for optimal results.