Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain a small painless sore over the lower lip can be a Herpes Virus infection causing cold sore, as it have an activity period of around two weeks and then slowly the sore disappears as the virus count decrease and the virus remains dormant over the skin surface which can reactivate at any point of time when the viral count increases or there is decrease in body immunity or there is exposure to virus.. You should consult a Dermatologist and get evaluated and a few investigations like viral culture, Polymerase Chain Reaction etc can help in making a correct diagnosis and in case of herpes antiviral oral medicines like Acyclovir, Famicyclovir or Valacyclovir can help in prevening further outbreaks as the antiviral medicines cannot cure the active infection and can only prevent further outbreaks.. Topical acyclovir ointments are also given as they decrease the viral count over the sore.. You should also be careful and prevent intimate contact with other individuals as herpes is contagious.. Hope this information helps.. If you find the answer helpful please give me a Five Star Review and click on found the answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora..