Most probably,you night have acquired Herpes simplex
type I infection(Herpes labialis),which occurs over the lips.
They occur most commonly due to fever
or any other disease which lowers the immunity.
There is no method to eradicate herpes virus from the body, but antiviral
medications can reduce the frequency, duration, and severity of outbreaks. Analgesics can reduce pain and fever. Topical anesthetic
treatments can also relieve itching and pain.
There are several antivirals that are effective for treating herpes.
Please consult your doctor and get it diagnosed and treated.
It is a self limiting disease,so don't worry.
Wish you good health