I don't know what you mean by "a little under the weather", but your chances of getting herpes from a one-time protected encounter are quite low, around 1 in 10,000.
Remember that it's still cold and flu season, and now we have Covid-19. You can have very mild symptoms of that, much like a cold, especially if you are otherwise healthy.
At 12 days without any blisters or sores, and with using a condom, I wouldn't worry at all about herpes.