I Have A Bump On The Inside Of My Left

I have a bump on the inside of my left butt cheek, near my anus. It would swell up, and then go away, but recently it appeared again, and I can feel the skin is getting thin. I went to the bathroom today, and when I wiped there was blood. So I felt around the bump and it was bleeding. I gave it a little bit of pressure and a lot of blood came out, and what appeared to be a blood clot. Now it is still bleeding, but only a little bit.