I noticed about 1 week ago a yellow patch (it forms an almost perfect circle) inside my cheek which has a red border. It is about 1cm in diameter. It causes me no pain at all, I only noticed it because when I was moving my tongue around it had a different texture so I checked the mirror. I went to the dentist to have it looked at and he didn't seem overly concerned about it, he said it is not "suspicious looking" (I believe he was referring to cancer) and that we would monitor it. At the time I was ok with that answer but I am really wondering what this thing can be?