I have had trouble with canker sores for years. I tried several different things and nothing worked. Until one day I decided to try chammoile ( I think that is how to spell it) tea.
I just wet the teabag with a little warm water and put it on the sore, it especially works well if you catch it right when you feel it starting to form. I just hold the teabag on the sore for about 30 minutes several times a day. That usually takes care of it, sometimes the sore will go away and not form at all, but for the times it does form, if you catch it right away there is almost no soreness at all.
Hope this works for you.