The risk was not very low, it was no risk.
I understand how you feel. I fooled around with a man about three years ago while I was in a relationship and he ejaculated on me getting it on my chest. Till this day I still worry about me having HPV from his sperm that got in me. I've read in multiple forums that it's a skin to skin STD and that there's no risk because it's INTACT skin, but I still worry. I've been STD tested, I even went as far as getting blood drawn last week to see if I got HSV2, and I'm clean! I think the guilt is what makes it worse and these forums. I'm trying to relax about it but I know exactly how you feel. Anyone else have any input in this?
I am still worried... Any more advice from anyone?
Mutual masturbation its a safe sex practice, not a risk for HIV at all, as for another STD's I think the risks are only theorical, I would not worry.