I'm a 17 year old male and I was recently diagnosed with Ulcerative Colitis. A feew weeks ago I noticed something near my anus... well actually right at the end of my tail bone. It's a round lump and its very hard. I can even move it around, like its just there under my skin attached to nothing. I'm very worried about what it could be and have been wondering whether its linked to my disease or not... any advice would be great!