What Causes Sensitivity And Redness On Penis?

About two years ago I was using a public restroom and I hit my penis on the toliet lid, ever since my penis has had a rawness feeling and super sensitive around the tip, sometimes it had redness sometimes none, it is very irratating and is easy for it to rub and hurt, I can't wear boxers anymore since that day, I'm 17 and I've never had sex or never masterbated, and I'm circumcised, what's wrong with me??