The symptoms you are describing sound most like a follicular abscess
or infection around an ingrown hair, but it is important to speak with your doctor
. These often develop in people who shave or wax their pubic hair, and are characterized by a small bump that is sore or tender to touch, which then spontaneously drains after warm compresses and usually shrinks and disappears. You should avoid shaving or waxing for some time, and try to use better razors in the future. You are right that certain infections, which includes herpes and HPV (or genital warts), can cause genital bumps, though these wouldn't usually improve with compresses the way that this did. It is good that you had all the testing done a year ago (and syphilis is definitely still around!). If you are concerned, it is good to bring up your concerns with either your primary care physician
or your gynecologist, who can take a closer look that the lesion and determine whether it is likely to be from one of these other infections or whether it is simply a draining abscess that should continue to improve on its own. I would also definitely recommend seeing your doctor if the lesions grows bigger again or if you develop increased pain, swelling, or fevers and chills.