Little League warming up require you to pitch?

[parrothead]

(Little League)If someone goes out to the mound (specifically the P from the inning before) and starts to warm up is he required to pitch (if eligible)?

If the answer is No, he does not have to pitch, then I have no follow ups.
If the answer is Yes, what if he is warming up and realizes he is injured or is arm is hurting, obviously nobody would want to require someone injured to pitch, but if removed from mound for injury, can he play another position?

I asked for LL specifically, but if there are any other variations for different governing bodies, that is useful as well.