Tiny Pimle on my penis, and 2 inside my meatus!

Hi. Recently, around 2 months ago, my girlfriend who I have been with for 8 months, who has no visual STD's, pointed out to me I had a tiny pimple, half way up my penis. Not on the shaft or the base. Lterally half way up it, and is so tiny, it is only visible when my penis is erect. It is very small.

 Then recently, we were having sex, and when i ejaculated, blood came out. Only a miniscule amount. I checked my penis after, and it turned out I had a TINY pimple on the inside of my meatus. I found this by opening it up, where I can see 2 of then on ether side. What had happened was, one of the pimples had burst and blood came out.

It is very strange as I looked at it again a few days later, squeezed it, there was absolutely no pain, and only blood came out when I forced enough pressure. It is also the exact same color as surrounding skin. I do worry that it is an STD however, but I do not understand how I would have caught it off my girlfriend, as she has no visual STD, and no STD at all as far as we are both aware. There is nothing surrounding the pimples, and they aren't a worrying color. They literally look just like little pimples on my penis. But I have no idea what they could be, as they don't seem to go away.

Any help would be fantastic. Thankyou.