Nick's trying to teach Michael how to act on his first time out on a girl: the rules etc. He's also fixed Ben's chair though Ben forbade him to ever touch anything of his ever again, and when he later tells Ben that he fixed his chair, Ben goes off into a rant about how he just wants him to leave everything alone. Susan just puts Nick latest behaviour of trying to fix things down to an awkward phase, but Ben disagrees: twenty years isn't a phase, it's him.