Mysterious bump on penis shaft.

For starters I'm 17, male, and have only been given a hand job/blow job from my clean girlfriend. I masturbate often also. Just recently I've spotted a growth or bump that is pinkish/skin colored and a bit firm to touch (size of a popcorn kernel and doesn't have a pimple head...) it's located on the shaft of my penis; right side about a quarter of the way up. It hurts, not extreme, when I push it or attempt to pop it. My question is what the hell is it? My girlfriend did have a canker sore at the base of her gumline, and the bump appeared possibly a buiseness week or so after the blow job. Could it be syphilis? I'm scared sh*tless right now...