Thank you for your inquiry. From what we gather from the question, you were asking about the possibility of HIV transmission from blood/bodily fluids on a piece of skin entering the mouth.
From the information given, this scenario is determined to be of No Risk (transmission is not possible in the given scenario). This scenario is determined to be of No Risk because it does not fulfill the requirements of our HIV Transmission Equation (see image below).
In order for HIV transmission to occur, HIV positive fluid (blood, semen, vaginal fluid, anal fluid, breastmilk) must have direct access to the bloodstream through a high, low, or sometimes negligible risk activity.
Although you mention the possible presence of bodily fluid and an open sore in the mouth, there is no direct access to the bloodstream. Additionally, any potential fluid on the piece of skin would have been exposed to oxygen, rendering HIV transmission nearly impossible. Dried or drying HIV positive fluid that is exposed to the environment such as being on top of skin or a couch is quickly rendered inactive, effectively making transmission difficult to achieve (1) (2).
Recommendation: No need for HIV testing with the scenario provided, refer to a healthcare professional for other health related questions.
AIDS Vancouver Helpline/Online, Nancy.
If you are satisfied with the Helpline service, please consider Donating