Hi, my 18 month old son banged his shin a few days ago. he has an average sized bruise on it and a lump underneath. should i get this checked?

Bruise with hematoma: The shin area is a very common location for a toddler to have a bruise from a fall. Sometimes, a small vein near the area of injury is injured as well causing a small hematoma or "lump." It should gradually get smaller over the course of a few weeks to months, but should no longer be painful after about 1 week. It should not affect his walking. If other symptoms develop, he should see his doc.