Red pump on the left side of my penis

A week and a half ago i noticed I had a pimple looking thing on the middle left side of my penis. It had a white top which i left alone. 2 days later i noticed it popped and was left with a red bump. It is raised above the skin and abit less then half a cm wide. It's not completely red as it has some faint white spots. I feel no pain and am sexually active. It can't be STD's because my gf was a virgin and i was her first and am her only partner. I'm also 17. I am going to leave it alone for the next 2 weeks or so just too see if it goes away. Does anyone have any clue as too what it could be?



Thank you