I doubt that you genital herpes. If it is the primary episode, symptoms occur 2-11 days after the initial contact. If the 'zit' opens up into an open sore then I may be a little bit more worried.
However it sounds like it could be a genital wart or if it's at the end of a pubic hair, it may simply being agitated and imflamed.
I wouldn't stress too much, but your better off going to your doctor and checking it out.