What Causes A Lump Along With Bruising On The Face Of A Child?

My son hit a the when sledding 3 weeks ago. He had what appeared to be a brush burn on his cheek and immediate swelling. The following few days the bruising developed and encompassed most of the side of his face and below the eye. The bruising has gradually gone away. However this week he bumped the same cheek at daycare and has a small bruise. As I questioned what happened and felt his cheek I noticed a pretty large bump on the maxilla that I didn't feel with the original injury. Is this bump a cause for concern? I don't feel it is due to the second "injury" at daycare.