You had the safest sexual encounter I can think of: oral sex itself is highly safe, and adding a condom reduces the chance of any STD to just about zero. Hand to genital contact is never a risk, regardless of recent cuts or sores on the hands. You can be certain the "pinlike bump" of your palm isn't herpes or any STD.
Further, no STD can cause symptoms in less than 36-48 hours. Whatever is causing the "blister" on your scrotum has nothing to do at all with the sexual exposure you describe. Without seeing the lesion, I cannot comment on whether it's a pimple, boil, herpes, or something else. (The term "blister" sort of implied herpes, but blisters and pimples look very differrent; you should be able to tell them apart yourself. Herpes of the scrotum is uncommon.)
Bottom line, to answer your closing question: You have no worries about STD from this episode.
Good luck-- HHH, MD
Bro, If you wore a condom for oral sex and did not have vaginal sex then you can't get any safer than that. The only safer option is not to have any sexual contact. ( i'm not joining the monestry just yet :O) You wont have picked anything up if that was your only contact,whatever is going on it isn't STD related,but see what the doc says.
Oral is really pretty safe, and with a condom, I think it's about as safe as you can get while still having a partner. No way you could get HIV from touching her, even with those cuts on your hands, and no way you could get herpes on your hands, either. I think you have nothing to worry about - your anxiety's getting the better of you :-)