What oils are good for getting rid of mouth sores?

Over the weekend, I developed a weird sore on the roof of my mouth, and it goes nearly all the way to the back of my throat.

It's so bad that I've been reduced to consuming liquids and soft foods.

Even drinking water hurts (and I drink only ozonated).

I wonder what could be the cause of this sudden problem. I was fine last week.

Help!