The experts on the doctor forum have some things to say about this. You are new here but you an always key word search the STDs forum in the Doctor section to discover tons of info on your own.
"There is some small risk of skin-to-skin transmission of some STDs through frottage, primarily herpes and HPV; but even for those, the risk is lower than with anal or oral sex. Mutual masturbation is essentially zero risk for anything. There is no realistic risk of transmitting HIV, HBV, chlamydia, etc. Syphilis is possible but unlikely. Oral sex is also pretty safe, by the way--but still riskier than frottage and mutual masturbation"
"we know that almost nobody gets STDs" by mutual masturbation. There is no reason or worry to "be careful where [your] hands go" or to stop and wash hands during the event."
"You are correct that mutual masterbation is very safe with almost no risk of STDs. The skin on the hands is very thick and not susceptible to infection. The presence of 2-3 small red spots on your hand (where on your hand, back, front?) without other symptoms is not suggestive of STD. I would not worry about putting your contact lenses in--just wash your hands well before you do, as is recommended for all who use contact lenses. "
I think it might be possible yes, i wouldn't rule out that possibility. I mean genital warts are contagious, even after touching them if you were to touch your lips or anus for whatever reason theres a chance of spreading them. Hpv can lie dormant for long periods of time before showing or may not even show any symptoms at all. If your partner doesn't have them i would worry about it.