Hello. Thank you for writing to us
I will keep a likely possibility of Herpes Labialis/Cold Sores. Herpes is caused by a virus, 
herpes simplex virus. 
Herpes labialis usually presents as a cluster of bumps on or on the area around labial mucosa,. These bumps may later become fluid filled, scab up and ultimately resolve in about a week.
Herpes may recur; certain well known stimuli that seems to exacerbate a flare are 
fever, menstural cycle, 
stress, exposure to strong sun etc.
The frequency of recurrences decreases with time.
For an episode of herpes labialis, I usually suggest an Oral 
antiviral e.g 
acyclovir or valacyclovir, for my patients of herpes labialis.
Oral antivirals are prescription drugs, I suggest that you visit a specialist for a confirmatory diagnosis as well as appropriate prescription.
Regards