Hi, Starting yesterday I began to experience a sharp soreness a the very base of the bone at the top of my buttcrack whenever I would do sit ups, despite the fact that I was on a thick gym pad. After some searching online, one of the most popular answers to similar problems was a pilonidal cyst . After a personal inspection, however, there is no skin discoloration or evidence of a cyst except the typical pinkishness (I m white) at the crease at the top of the crack. Furthermore, the soreness is originating from what feels as hard as bone, and is touching the bone, but feels like a small lump at the base of the bone. So my question is, can a pilonidal cyst start as a lump with that description, or is this a typical bone shape, and I have just irritated it with a 2-or-3-times-per-week ab workout (many times only on a yoga mat on a hard floor). Thanks!