Me?
Doesn't sound like a fast break was happening...I would have stopped the game and got the kid a sub.
Certainly don't allow the injured player, who's holding his head, to have to wait very long to get him out of the game.(ankle injury may be different say during a fast break for the other team)
If he's bleeding, stop the game pretty quick...it takes to long to clean up every spot of blood on the court.
Better to error on the side of caution, when a player's health is concerned...IMO.