I think you need 2 sprites - Hand (just a rectangle) and Wrist.
Set Origin image point to the right end of the Hand sprite, and pin your Wrist to the left end of the Hand sprite.
Then simply change the width of the Hand sprite using Sine or LiteTween bahavior.
Edit: on the other though, Pin bahavior will not work here, because Origin point of the Hand is not moving. Still you can simply change Wrist position and angle to Hand's left end position on every tick.