Can you get HIV if someone fingers you with a fresh scab (five hour old cut) on his finger just on the outside of your vagina for a few seconds?

Extremely unlikely. There's a lot of fear and anxiety regarding HIV. From what you describe, I would describe this activity as extremely low risk. First of all, your partner would have to be HIV positive, second they would have to be untreated, third there was no active bleeding, and finally this did not seem like a contact of real concern. It's always good to talk to your partner(s) before sex and your doc can help2.