How To Treat A Jelly Like Sack Outside The Rectum?

hi i have a jelly like sack just outside the rectum(under the skin) it doesn't hurt. I thought it was a pimple @ first but it never amounts to an ything. it started out about the size of a pea and now it's about the size of a jelly bean. i've had it for just about a year just wondering if you could possible tell me what it could be and what i would have to do to get rid of it. I also had a mole on the inside of my thigh that has the same thing but this ones hard and sometimes sore but doesn't amount to anything either.thank-you