I have a 3 year old with a sore in his mouth. What is it? What can I do before!

I have a 3 year old with a sore in his mouth. What is it? What can I do before we get to the doctor?

It is between his upper lip and his gums at the very top. It looks like a white circle and it has a red streak coming down to his teeth. All of his teeth are clean and we brush them about once everyother day (I know it should be more often, but he is 3 and he runs).

Please help. Thank you.

If this white area is an ulcer most likely it is a cold sore (Herpes simplex) or Canker sore (unknown cause). Sometimes a cold sore can be very difficult the first time. When children are first exposed to herpes simplex their first outbreak is often multiple lesions in the mouth and on the lips or it can be just one larger than normal one. However, it could also be a canker sore which may have been caused by trauma during brushing when the plastic of the toothbrush hit his gums b/c he was squirming and this can induce a ulcer like this. Just try and keep it free of bacteria, use hydrogen peroxide you can gently put a little on w/ a Q tip. You could get some topical anesthetic like ambesol to put on it but it might burn a little at first.