"Of course it hurt you hit me with a metal fist! I was expecting flesh and bone!!"

He sits up and rubs his jaw emphatically, apparently having completely forgotten he asked for this and he was also going to attempt to heal himself.

"...That's a pretty impressive prosthetic. Most prosthetics I've seen and made don't have any functionality. They're just fist shaped lumps of steel. You actually have control of that thing, don't you."

Yup, he's totally forgotten the purpose of this.