Welcome to the HIV forum. First, despite her history, the chance your partner had HIV is low. Even among sex workers (in the US), HIV is pretty uncommon in women. But since you're nervous about it, you should aks her to be tested, if she hasn't done so recently. If her HIV test is negative, you're home free.
If it happens she has HIV, then catching herpes from an HIV infected person indeed is a pretty high risk exposure. However, in this situation "high risk" means one chance in a few hundred, so the odds still would be strongly in your favor.
Of course, whether or not your penile lesion was herpes also is unclear. If initial genital herpes causes symptoms at all, usually there are multiple penile blisters and sores. However, a single lesion is possible, and the location you describe indeed could happen despite a condom, i.e. skin contact above the condom coverage are. You should see a health care provider about it. If the lesion has healed, blood testing could tell whether or not you are infected.
Bottom line: See a health care provider both about the cause of the penile sore and to discuss HIV testing; and talk to your partner about having an HIV test. In the meantime, don't freak out. For all the reasons above, the chance you caught HIV is extremely low.
Regards-- HHH, MD
Im not hijacking this thread with my own Scenario, im just curious about a part of your response to Joel.
You regarded catching herpes from an HIV infected person indeed is a pretty high risk exposure.
Would the fact that the other 3/4s of his penis (inc Urethra) is covered by a condom not still constitute low to zero risk?
If Herpes did show up on the shaft/base of the penis the next day, how would HIV have entered the person?
Maybe i misinterperted your response, but some clarification would be nice.
Regards.