Welcome to HCM.
infection around mouth can occur to anybody. It is not necessarily a sexually transmitted infection. It is a self limiting disease and you will be alright within a week or so. Recurrence of the lesion once in a while is possible.
It is not related to HIV
. If it does not heal after a month, then there may be a possibility of immuno-suppression.
If you have a risky sex behavior, then you can have a HIV screening test. Otherwise you need not worry at all.
Get well soon.