Infected hair follicles since masturbation?

I'm 22, and recently began masturbating after learning the...joy of it from my last girlfriend. The problem is that I think the friction is irritating the shaft of my penis and causing small, pustule-like bumps. They tend to burst and go away after a short while. However, there is one that is large and hasn't gone away. My understanding is that these bumps are caused by friction and not a big deal, but how can I treat it and get rid of it?