When you say "right after" sex, how long is that - a few hours, a few days?
How long have you had them?
Herpes sores wouldn't appear for 2 days, at a minimum, and the chances of you getting herpes with a condom are very low.
You should let a doctor see it, though. It could be folliculitis, an allergic reaction to something, dermatitis, or a list of other things.