There's no argument and it's unclear whether he takes it as a sign he really needs to be sorry or not. In any case it doesn't start a row, which is a good thing. He appreciates the help and the way it's given, as it allows him to retain some amount of dignity at least.

Remus' final question stills him and he has to think about it, not looking at him. On the one hand being in proximity to Remus makes him feel ill not because he's disgusted with Remus but because he reminds Regulus of the fact he'd done things to deserve the ire he'd received. To not be trusted. On the other hand...

He exhales shaking, hand settling at his own nape and digging blunted nails in slightly, grounding. The potions they'd poured into him for treatment leave him a little fuzzy but finally, finally, he nods. "I don't want to be alone."

It's not an admission of wanting his company in particular now that he's past the traumatized shock stage, but it's something.