I Recently Had An X-ray On My Left Shoulder Because

I recently had an x-ray on my left shoulder because I have a bump sticking up on top of my AC joint. The bump only hurts when palpated. When I had an MRI, the AC joint looks normal but there is a black spot where the bump is in the AC joint. I had a cortisone shot recently. Is the black spot in the joint likely the cortisone?