zoster isn't sexually transmitted. Zoster is shingles. This doesn't sound like shingles. Shingles tends to linger for longer than a few days and is rather painful, not just painful to touch.
since your rash is gone, no way to figure out what causes it. It wasn't herpes simplex causing you those symptoms in that area.
should your rash reoccur, be seen promptly for an exam by a medical provider.
grace
By the way I posted this in the hiv forums but it was moved here
I was really wondering if it could be hiv infection causing that