I've Noticed A (roughly) Centimeter In Diameter Skin Colored Bump

I've noticed a (roughly) centimeter in diameter skin colored bump on the bottom half of my shaft so naturally I tried to pop it and it just got red.. anyways I can't pop it with just my fingers or at least I'm too scared to. I haven't had sex in weeks so I wouldn't think it was an std because it is something the popped up recently. I don't know what it is, for more info it looks like there's a small indent near the center and I believe it's been there for 2 days.