Hi and welcome! I have been worried over those little guys before too. Rest assured though that it is probably one that is simply doing it's job....fighting off a small/local infection or a virus.
Lymph nodes under the chin can indeed be a result of an infection of the mouth (teeth or gums) so going to your doctor and dentist is a great idea. Some people have even had a lymph node swell due to cystic acne, so if you have any signifigant blemishes, these could be the cause.
I even had a big node behind my ear swell once as the result of an allergy to hair color! Even after the allergen/infection/virus is cleared up, it may take up to a few weeks for the nodes to go down to normal size.
Again, try not to worry, and go consult your dr, so you will feel better.
Welcome, and post anytime:)
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"It is when we are most lost that we sometimes find our truest friends"
Panic Syndrome recovery due to CBT