A few pimples on penis? STD? Nothing to worry about?

Hi all,

I noticed a few small, reddish, pimple-like things/papules on my penis the other day, at the top of the shaft, right before the head. There are 4 in total, pretty close, but not clustered together like a lot of STD symptoms I've been looking at. They also don't hurt at all, aren't irritating, sore, etc. I do have sex with my girlfriend without a condom. However, she recently got an IUD, and they had to test for STDs before she got it, and she didn't have any. And she doesn't have any pimple things. With that in mind, I hope I'm just being a hypochondriac about this, and was hoping I could get some opinions, before seeing a doctor (which I do plan on doing).

Since my girlfriend got her IUD, occasionally during intercourse I'll be able to feel the thing (string?) when I'm particularly deep, and it's kind of a sharp almost-pain, like I'm getting jabbed. It also occurs on the right side, where the pimples are as well. I thought maybe it was an irritation or injury from that? Also since she's had her IUD, on occasion, she's had a more difficult time lubricating at first, so I thought maybe it could be an abrasive irritation from that? I'm hoping it can be explained by one of these things.

Anyway, as I said, they don't hurt or anything, and I don't have any other symptoms that I've come across while researching what they might be, but I'm still freaking out a bit. I'm really hoping they're just papules from irritation, or ingrown hair follicles or something, rather than genital warts or something. All insight onto what this could possibly be would be much appreciated.

Thanks,
mouse