Injured Player Sub/Free Throws

[rekent]

Want to make sure I got this right:

A1 is fouled in the act of shooting, awarded 2 free throws. As a result of the foul A1 hits the ground hard and injures his elbow, coach quickly comes out on the floor. At this point, coach has two options:

1) call a timeout to keep A1 in the game if A1 is able, or
2) substitute A6 for A1, A6 will shoot A1's free throws - (here is where I am unsure) is A1 eligible to return to the game after sitting a tick depute being removed and another player taking his free throws?.

I know I have heard that somewhere, but can't remember where and if it applies to NFHS or not.