4 mths ago, I feel on the bathroom floor. I have a hematoma, bulge & large dent on my buttocks. Can plastic surgery help?(Photo)

This is a common reason for which  I see patients in consultation. Trauma or injections to the buttocks can cause some of the fat cells to not survive and therefore you end up with a depression in the area. The contour is restored with fat transfer to the area. Many times this can be accomplished with one session, but sometimes it requires two or three sessions of fat grafting depending on the scar tissue present to get the contour perfect. I hope this helps and best wishes. 

As you've said, a hematoma went on to develop scar tissue  that has shrunk down and pulled in the surface of the skin.  The treatment is to first release that constricting scar tissue through a small incision and then to immediately transfer fat into the relaxed space to restore contour.  Fat graft without scar release will not correct the problem as effectively.

trauma is sometimes associated with destruction of fat cells and create deformities.I  would like to see the other buttock cheek, but I think that some fat grafting to that area of depression would help to correct the deformity, it mat be able to be achieved in 1 procedure, but additional procedures may be necessary to achieve  the result that you desire. Also I would wait for at least 6 months after the injury before starting on the corrective procedures. Norman G. Morrison MD