My 20 month old son has a Hugh white sore on his bottom of his lip. It does not seem to bother him and it is not an open sore. I don't think it is a canker sore because he had it for about a week now and it has not opened. I tried looking at it today and he didn't seem like he was in pain. He also eats well and chews without pain. I am worried, and will make an appointment for him on Monday, but I thought that maybe someone had this happen before? Thanks in advance.