"It's nothing." He was going to try and downplay this as much as he possibly could. Even if he hadn't have thrown the first punch, he still wasn't justified in hitting her own brother. If it was anyone else, he wouldn't have been so... deceptive? about it, but the fact that it was Shane brought in a whole new element.
When she climbed on top of him, he leaned back a little, giving a small "mmmph" when she wiped his nose. It was a little tender.