Possible mouth sore solution

I just had a very bad mouth sore 2 weeks ago. It was on my gum and upper lip. I did not have anything to cure it but sufferred for two weeks, then it cured by itself. I would like to know the staff you mentioned, should it be used when you have a mouth sore or it can be used to prevent it happen? How many times you have to use it every day? More information please. Thanks!