The Doctor nods again, accepting as much information as he can get. Then Nick makes his last statement and the Doctor chuckles softly.

"You're talking to the wrong person if you want to know that. I mostly travel with humans because they understand things I never could."

He's not being entirely honest. It's not quite false modesty, it's more than he's aware there are some things that he will never understand about humans.

"So he's found a new group to hang with. And they approve of his new behaviour...." He trails off in thought. "Nothing for it, use this place and this time to regroup yourself. Rest. Nothing you can do about him here, unless he shows up. But taking care of yourself? That should be done."