Sans does wince, at first, when S-4 takes his arm. But he also makes no move to pull away, because he trusts that the pain is temporary. He trusts wholeheartedly now that S-4 will be able to heal him.

Sure enough, scant seconds later, he feels that familiar warm rush spread from the site of the wound, all up and down his arm, and then all throughout his body to suffuse the rest of his bones. From there, S-4 will see no sign of pain on Sans' face. All he'll see is an expression of heartfelt relief, even if Sans keeps his eyesockets closed until S-4 is done. Tension is bleeding out of Sans that he'd grown so used to that he'd forgotten was even there.

When S-4 pulls away, Sans immediately moves to unwrap the bandage. The sight revealed beneath is an entirely unsurprising one. Where scant seconds before there was a neat but painful hairline fracture, now only whole and undamaged bone remains. Sans regards his arm with a shaky smile for a moment, and then he slumps back heavily against the couch with a long sigh of relief.

"wow..." He chuckles, a little shakily, lifting up a hand to rest over his eyesockets. "wow, i forgot how good that feels. thanks, bro."