Colon cancer concerns?

Pardon me for being graphic but… I was wiping my rectum the other day and noticed a lump right on the outside of my rectum. It is unlike any of the tissue around it, a lot harder and denser. It is between the size of a bb and a pea. I have no family history of colon cancer that I know of, and my bowel movements have been normal (or at least as normal as they can be given the shitty dining hall food I have to eat and the shitty beer I have to drink). Also I’m 20 years old. Should I be concerned about this?