I think you are detoxing. The oil itself doesn't have properties to cause this to happen. Either it was on it's way to happening when you started, or the oil is working hard on the bacteria in your mouth.
That sounds like an awfully big sore. I would definitely put something on it, like collodiol silver and definitely add some oregano oil to your pulliing oil.
Yes, it happens. We've heard this before. I would say, major detox. Be very careful though, a major infection in your mouth can affect the rest of your body. If the thing doesn't go away (and I'm saying that because it's so big) I would think about Antibiotics . I don't mess, ever, with an infection in my head. But that's AFTER you've tried natures Antibiotics .