I'm still laughing about digital. I'm guessing she just used a couple of fingers?

OK, condoms do protect from STDs, but they only protect the part of the penis that's covered, and the base usually isn't covered. That being said, unless she had a scalding case of herpes and you didnt know it, it's more likely that that's just a zit. Those happen a lot in that area where all those hair follicles and oil glands are. A herpes or other sort of STD lesion would take longer than two days to show up (viral incubation period is 7 - 10 days), and with an initial herpes outbreak you'd have other symptoms, too. If it's worrying you a lot, definitely go to the doctor.