Red bump on penis shaft Help!

Dear Doc

It kind of looks like a pimple, pinkish in color, but there is no pus. it is round. It's on the underside of my penis, middle of the shaft. It is painless. I thought it was either a pimple or ingrown hair but its been over a week and hasn't seemed to change in size.I did have sex around a week and a half ago, but I used a condom. They spot where it is would've been covered by the condom. The bump showed up a day or two after sex. I wouldn't think anything of it if i hadn't just had sex and because of the sex, I am more worried. I don't think it is herpes because it does not hurt, it has not turned into a painful blister, and I have not had any itching or burning down there or anything out of the ordinary. I've been putting neosporin on it, and it seemed to change the bump to more flesh colored. I'm not sure if the size has changed or not. I'm freaking out! what is this?!

Thanks