Very large swollen canker sore

[Guest guest]

Last night my son developed a large swollen canker sore right on the

inside of his upper lip. He has had a nose cold for the past couple

days (no fever or cough, only runny nose), and I gave him a granny

smith apple for dessert, then the large sore appeared. It was also a

very little bit bruised (black and blue) on the outside skin above his

lip. I didn't take him to the doctor yet and he went to school today.

Can anyone recommend a treatment for this? Thank you!!!!Trixie