I have a hard lump deep inside my right buttock about 4 inches below my back. It is painful if I sit at a particular angle or press on it. There is no protrusion to the surface, it is deep. There is also a colorless, semi-puckered scab on the skin on the surface of the buttock. I know Breast cancer tumors can elicit this scab. I am wondering if this could be a tumor?