Thanks for your query, I have gone through your query. The soreness over the bottom lip can be because of the herpetic infection or it can be a aphthous ulcer. Nothing to be panic, consult a oral physician and get it evaluated. Mean while you can take symptomatic treatment like topical anesthetic like lignocaine, and topical analgesic like choline salicylate. It is a self limiting condition, no need to take zovirax, because it will not be effective if you take this medicines 24hours after the onset of the lesions. I hope my answer will help you, take care.