Hello,
Cold sores is caused by HSV1. You can use some OTC anesthetics like lidocaine or benzocaine for pain relief. Treatment with topical acyclovir or penciclovir will reduce healing time and decrease pain associated with the lesion. Also you can use oral antivirals. I suggest you to get them prescribed from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.