I don't know if it's acne, pimples, or something else.

Sometimes the back of my neck and the tip of my head swell.

It looks like a pimple, or a blemish, or something else entirely.

Actually, I've never been to a hospital before, so I don't know what it is.

You just happen to come across it and find out about it, and after a few days, it just disappears and you forget about it.

It doesn't hurt unless you touch it, and there's no particular discomfort unless you squeeze or press on it.

What is this?