Hi, I have a small pea sized hard lump at the top of my bum crack . The lump itself doesn t hurt all the time, mostly just feels like my tail bone is bruised but can become so painful and uncomfortable that I can t even sit sometimes. The pain and uncomfortable part has been going on for about a year now. But i just noticed the lump a couple months ago. From when I found it, the lump hasn t changed size at all, but is always there pain or not. What is this lump?