no leave it alone. if you break the integrity of those blisters you will be releasing even more viruses that you may inadvertently spread. the best care would be to help the lesion dry. avoid touching it if you can. don't let anyone drink after you and avoid kissing. some people use prescription acyclovir topically or orally but that would depend on the severity of your fever blisters (herpes simplex) and the frequency in which you get them.
should i pop a fever blister. once you feel a fever blister developing should you pop it? whats the best way to care for a fever blister?