Is it a canker sore or what?

Well for the last week I had a sore on my tongue. It hurts Altot especially when I am attempting to eat or swallow. It cause so much pain that I have trouble sleeping. I googled information about canker sores but I'm not exactly sure what it is. I have been eating alot of yogurt because eating anything else hurts. What do you think it is? What should I do?