"Oh."

Whatever answer he may or may not have been expecting, he apparently is just fine with the one that she's given.

When she brings up his arm, though, his mouth twists slightly in a reluctant little grimace as his organic hand moves up to squeeze at the spot where his automail connects.

"... Mm. It's not joints..."

But oof it really is smarting. Despite the reluctance in his voice, he does take a couple of steps forward, which are as stiff and awkward as the wave was. He looks way too young to be arthritic, though.

"What's a heating pack?"

The first thing that comes to mind is like... a backpack but warm? Or something?