Hi thanks for posting,
Your doctor has diagnosed as cold sore
labialis.it is reccurent disorder as the virus responsible stays in the ganglions after initial episode.It commonly occurs on the lower lip
you have had valtrex
in adequate dose. so the risk of transmission is less
you had a prior episode of the same but normally it heals without a scar , so you can confirm your diagnosis by lab test.
hope this answers your query