It takes John a moment to process what happened. He has to regroup from the pain himself, to put effort into clamping down and keeping his expression neutral so Ianto doesn't freak out, to try and guess by the feel of it and limited movement how bad the bone damage is. So John isn't looking, exactly, at Ianto when his handle convulses before he lets go. He's half assuming it's in response to something he's done, until he glances up at the shaky breath Ianto takes before opening his eyes.

Ah.

"Shit," John says emphatically. Then: "Don't worry about it, I can do it myself it'll just be slow going. Give it to me."

The cloth you were going to use. It's fine, he'll make do. It wouldn't be the first time he's had to treat his own injuries, after all.