The skin is a very effective barrier against HIV. Once outside of the body, HIV is quickly damaged and rendered unable to infect. Additionally, the body's immune system works incredibly fast at healing cuts, scrapes, and other wounds from the inside. For HIV to infect, it needs to have contact with the bloodstream, not only blood. For active, viable virus to gain access in sufficient quantity and concentration so as to infect does NOT happen through what you describe as "fresh sore finger".
-JC-
Thanks for your comments. Anybody else with comments.
I had just posted asking same thing - check my post HIV Transmission Through Gym Equipment.
Hope can give you some idea.
Anyway, I am still scared as you, because I read contraindicating info online. Some say HIV dies when exposed to air, some say it can still be active for a few minutes.