That beautiful aloe plant sitting on your sill has some quite potent curative powers. A little aloe juice from the juicy inner portion of the leaf rinsed over the canker several times daily could be just what you need.
You can also combine 1 teaspoon salt, 1 teaspoon baking soda and 2 ounces hydrogen peroxide. Mix and rinse your mouth with it four times daily. If the taste is too strong, or the tingle uncomfortable, dilute with 2 ounces water. You can also just rinse your mouth with lukewarm salt water. Or, if you're brave, just apply a little salt directly to your wound.
Sage is another option. Used most often to spice up turkey stuffing, this herb can be used to calm an angry canker. Simply add 3 teaspoons sage leaves to 1 pint boiling water. Steep, covered, for 15 minutes. Rinse your mouth with the liquid several times a day. You can also rub sage leaves into a powder and apply them directly to your sore.