Your son has a claim for negligence against the driver, who "bumped" him.  The driver's insurance carrier is liable for the injuries your son sustained including his medical bills.  When your son completes his medical treatment although it may seem to be minor injuries, you should obtain the medical report documenting the nature and extent of the injuries which will determine the amount of compensation for pain and suffering.  If your son is under 18, you would be handling the matter for him as guardian ad litem.  Guardian ad litem is a parent or guardian, who handles the affairs of a minor as the minor would not be able to represent himself in legal matters.