You didn't have a risk. Using fingers for penetration does not infect with HIV. In an adult, the only way you have a risk is through unprotected anal or vaginal sex using your penis without a condom. Also, sharing drug needles with infected users is a risk. Using your finger is not a risk, even if you had a paper cut or busted cuticle or whatever. It's still not a risk.
Sorry I didn't reply in Spanish. I read it better than speak it. I'm sure you can find an online translation tool if you don't understand my reply.
You can't acquire HIV from inserting your finger in to some one's anus even if he was HIV positive. Despite of having superficial cuts on your finger and it coming in contact with the infected blood, it is not a risk.
No one has ever contracted the virus in that manner, you are not going to be the first one. Not an HIV concern. No testing needed.