mysterious bump!! TMI

So I've had this mysterious bump for about a week now... there is no head on it, but it's very hard when i touch it.. I have no idea what could've caused it. I'm kind of thinking it's chafing because I've gotten chafing bumps before, but they went away in 2-3 days. Do I need to see a doctor? Or should I just wait it out and see if it goes away?