Welcome to the forum.
You are at absolutely no risk of any STD from this sort of exposure. They call them STDs because you must have sex to transmit them -- indirect contact of the sort you describe is risk free. Even vaginal fingering or masturbation by a partner, even with vaginal fluids as lubricant, almost never transmit STD.
So no risk, no worries, no need for testing; and if you have a regular partner, you can safely continue your normal sexual practices without any fear of putting that person at risk.
I hope this has helped. Best wishes-- HHH, MD