Alum

I had braces growing up like most of us poor saps did, and constantly suffered from canker sores. The brackets would always cut my lip and sure enough a canker sore would appear the next day. I never found much relief from over the counter products, and to this day I still will get a sore if I even think about accidentally biting myself (and no smart asses, I don't have oral herpes).

I'm not sure when my mom learned this, but she taught me to put a little dab of alum right on the sore and it would magically disappear. Alum is a chemical compound like salt, and is most popularly known as a pickling agent. You can find it in any grocery store in the spice aisle. It stings like crazy but it literally pickles the sore. Hold out your cheek or lip, place a dab of the powder or granules (power is easier), and let it sit till your saliva dissolves it. Reapply about 3 times a day. That owie will be gone in no time, sparing your body of ingesting those extra chemicals in a medication.