My son has a lump under his chin?

Probably lymph node. There are several lymph glands located within the structures of the neck & will vary in size from the size of a pea to much larger if stimulated.When stimulated they can enlarge quickly and feel tender to touch or compression. A visit with your dr during regular hours should separate the simple transient issues from those needing further tests.

Related Questions

My son has a hard lump under his chin, which has been there for about 3 weeks now. He was put on augmentin (amoxicillin and clavulanate) for 10 days but its still yet to go away.

Time to see his doc. "hard lump" could be an abscess that needs to be incised and drained. You may need an ENT referral to get a better assessment if your primary care doctor is not sure. An ultrasound may be also required. Read more...
Not bacterial. There are other conditions in the differential diagnosis that are not related to bacterial infections and therefore would not respond to antibiotics.. For instance a sebaceous cyst would not respond to Augmentin (amoxicillin and clavulanate) and would need to be surgically excised . A calcified hematoma is another condition that would not respond. Read more...