Thanks for your assistance. I will update my results accordingly.
Regards
The sort of lesion you describe does not seem like herpes, which generally does not cause such a firm bump that cannot be popped. Also, although a single lesion is possible, initial genital herpes typically causes multiple lesions.
So herpes seems unlikely, but there is no way to know without clinical evaluation and lab testing. Direct testing of a lesion for HSV by culture or the polymerase chain reaction (PCR) is the most definitive diagnostic method. If the lesion becomes an overt pimple, i.e. a white head with expressible pus, or if it turns into an open sore, see a health care provider immediately for testing. If it doesn't progress that way and just heals up, the back-up approach is to have a type-specific blood test for HSV. Four weeks would be too soon; such tests take at least 6 weeks and often up to 3 months to become positive.
There is a much lesser chance, but not zero, that your lesion is due to syphilis. As for herpes, get immediately professional evaluation (preferably from a public health STD clinic) if the lesion develops into an open sore. Otherwise, have a syphilis blood test along with the HSV test in a few weeks.
Good luck-- HHH, MD