I didn't notice that he bumped his head at first, and thought he was distressed over the dog, but after rewatching I have to agree that he seemed to be mostly focusing on his head. Even if it looks like that though, I wouldn't say he doesn't care necessarily, he just might not be the type to freak out outwardly.

I'm glad it was okay, too. That would be scary, though I don't really see how you could just forget the dog.