I have had a boil like swelling on my anus going into my anus for about a week. It has a purplish and reddish color to it. It has a firm core that moves around. It has swell the size of a man's thumb. it has shrunk and back down to the end joint of a pinky. It increases the size when I sit on the toilet. When I stand up it will decrease in size. it hurts when I sit on the toilet. I'm just sitting in that position not having a bowel movement.