I have a small pimple looking bump inside my anus, just one and its inside not on or around anus, you can't see it on the outside. what is it?

Down Periscope!!: Very interesting. I'd like to know how you discovered that little gem...Anyways, it's probably a normal structure, like a sebaceous gland. As long as it doesn't hurt or start getting bigger or irritated, there's nothing to worry about. In case you do get worried, then you'll have to get an exam. The doctor will use a small device called an anoscope to get a good view.