As an adult, the only risks for HIV are:
1) having unprotected, penetrative vaginal or anal sex, or
2) sharing IV drug needles with other IV drug users.
NOTHING else you can think of is a risk for HIV, including the event you described. You do not need to test at all for HIV, since you were not at risk of contracting HIV.
Sorry for another question. Is the perianal abscess or the opening of an anal fistula considered as an open sore/wound? Many thanks in advance.
So, the way you get HIV was explained to you. What you write about in your post is not a risk. Even with the fistula. A wound has to be wide open, gaping, emergency type of wound to ever be something to even worry about. You did not have a risk and should move on.