did i get a cold sore from my dentist?

I have not had a cold sore before (and none of my family have) i went
to my new dentist who gave me a filling a week ago (which is still
hurting) and on the same side of my mouth a cold sore has appeared in
the corner. it is absolutely hiddeous and i cant believe i have got one
at 29 for the first time. Could it have been from the dentist somehow?

.