Player injury

[JLC]

What do you do when a player goes down injured as the other team is going the other way on a fast break with an obvious advantage and a high likelyhood to score. You see no blood or obvious broken bones on the injured player. I would think you wait until a dead ball or the injured player's team gets possession. Is there a place in the rule book that tells you what to do, or does this fall under the "official's discression" category??