Kenalog ate part of my body leaving it very painful

I have had stabbing pain in the s/i joint radiating up into the left illiac crest and down into the buttocks for a year.  Sitting is the posture of pain.  I had a Kenalog injection a few months ago, and a crater now exists at the site of the injection.  There is no tissue left between the skin and the bone.  My pain has doubled, and the skin feels like it is pulling and cold on the inside where the Kenalog ate my tissue.  What can be done about this?