MY 17 SON WAS WORKING ON TRUCK AND FORGOT A REARED BACK AND HIT HIS HEAD ON THE TRAVEL TRAILER HUTCH..HURT, GO?

AFTER HE HIT THE LEFT SIDE OF HIS HEAD HE HAD A LARGE KNOT COME UP..THE NEXT DAY AND EVEN TODAY (2 WKS LATER) THE KNOT IS STILL THERE AND STILL TENDER TO TOUCH...THIS SEEMS UNUSUAL TO ME HOWEVER, HE SAYS HE'S OK "MOM"..BUT IT WORRIES ME..ID THERE A DR. OUT THERE THAT CAN GIVE SOME ME INPUT OF POSSIBILITIES ON THE SUBJECT?..COULD THIS BE A INTERNAL THING THING THAT NEEDS TO BE CHECKED OR X-RAYED? OR JUST LET HIM BE..? I'M MORE WORRIED ABOUT IT THAN HE IS .(BY THE WAY I'M NOT SHOUTING, I HAVE TO TYPE IN CAPS BECAUSE OF MY EYE SITE..SORRY AND THANKS AHEAD OF TIME)