I have a dime-sized sore on the inside of my upper lip. It is kind of yellowish white surrounded by red, which I know is typical of canker sores but it is very large and has caused my upper lip to just below my eyes to be slightly swollen. This isn't like other canker sores I had as a child. It is causing me a lot of pain around the gums directly above my front tooth. I have a small filling between my two front teeth which my dentist said could cause sensitivity periodically so I thought I was having tooth pain about four days ago. Yesterday morning when I woke up my lip was swollen and there was this huge pocket inside my lip. I gargled with salt water yesterday but today it is slightly more swollen and more painful. Is it likely that it's a canker sore or something else? What can I do about it?