I'm 20 years old and I first saw this bump on my penis almost 2 months ago, I've never had anything like this before until now. It's on the mid area on my shaft, it's small, barely noticeable (it does get a little bigger while penis is hard), there's no pain at all and no irritation (even when I touch it), no redness on the skin around it, no tiny spots on the bump, and hasn't spread anywhere else yet.

It just looks like it's full of pus, just like a pimple, I haven't tried to pop it or anything, but it's always there, soft and hard. I do shave my pubic area, but I don't grow any hair on the area where the bump is. When I run my finger across it, it has sort of a hard feeling, not very smooth. The bump looks round, like half a sphere, and no flat surface. I've been keeping it clean, but it doesn't seem to be going away.

I am sexually active with my girlfriend that I've been with for 8 months, but she swears up and down that she doesn't have anything. I've been with 4 girls in my life, but I didn't have sex for over a year until I met my current girlfriend.

Could it be a cyst? I'm starting to worry a little bit and any information before going to the doctor will be greatly appreciated. Thank you.