How to tell if my canker sore is healed or infected?

Pain: A canker sore usually heals in 7 to 10 days. They rarely become infected. If your think you have an infection, have a lot of pain, or the sore does not heal in 10 days you should see a dentist and find you what is going on.

Eating is difficult: The sore may be painful for 3-4 days, but complete healing usually takes10-15 days. Canker sore usually doesn't get infected, but may recur many times each year.