There is no risk here. The skin on your scrotum is thick enough for germs to not penetrate, so things like HPV, herpes, and syphilis aren't a risk.
Gonorrhea and chlamydia are only transmitted via penetration - oral, vaginal or anal.
HIV, Hep B and mycoplasma are only transmitted via vaginal or anal penetration.
You're fine and have no need to test for anything, and no need to worry.