Thanks for your query.Based on the facts that you have posted it appears that you have
developed Staphylococcal infection
of the lip and tongue following oral sex.
Looking at the sequence of events during sexual encounter that you had with your girl friend possibility of acquiring STD can not be ruled out.
Please get your blood tests for STD done,
Please take antibiotics like Erythromycin
for a we .
Observe to have proper oral hygiene
by having saline or Betadine
gargles twice daily,