The only risks for HIV in adults are:
1) Having unprotected (no condom) penetrative anal or vaginal sex, OR
2) Sharing IV drug equipment with other IV drug users.
A pin is not an intravenous needle. You have absolutely zero risk for HIV, and there is nothing you could add that would make it a risk for HIV. I don't know why you think your brother might have HIV, but he should get tested if he's had a risk. Otherwise, I'm not sure why you even mentioned him.
In any case, a pin prick is NEVER a risk for HIV.