Cold sores can be caused by stress but what really causes them is a virus called the Herpes virus but being stressed out can cause a cold sore to break out and appear.
You can get rid of a cold sore by applying some baby orajel to the cold sore which will help numb the pain from the cold sore and help to get rid of the cold sore within a few days.
They also make medicine for cold sores but I hate the taste of the cold sore medicines and use baby orajel instead.