Exercise your arm/body part

I would like to know how to say “exercise your arm,” or it could work with any body part really, in Spanish.

In this case it was a nurse giving a shot to a patient, and then telling him, “it’s important that you exercise your arm that received the shot.”

Would the verb “ejercitar” or maybe “hacer ejercicios” work here? Or are those verbs used more for describing exercise to tone muscles? Would it be better to just say “mover el brazo”?

Es importante que usted ejercite el brazo que recibió la vacuna.

Es importante que usted mueva el brazo que recibió la vacuna.

I tried to say “ejercitar el brazo” and the (Mexican) person looked confused, so I switched to “mover el brazo” and they understood.

Is “ejercitar” not used like that in Spanish then?