I Have Mid Right Buttock Pain Around The Area To

I have mid right buttock pain around the area to the right of the coccyx. It goes under the leg and into the groin. It feels better if I put a tennis ball in the area an lie on it. That gives some relief for a while. In March of this year I had a radical hysterectomy due to colon cancer in the ovaries. The butt pain has just occurred, however, within the last few weeks.
I got great rellief from a chiropractic adjustment, but it reccurred in a few days. Hurts most when lying down or sitting.