That Sherlock was actually leaning against him was all he needed to know that he was really besides himself. Not that Greg didn't like it, cause, strangely, he rather did and even tightened his grip a little more to keep the other man close, but the other man really had to be out of it to allow himself to get so personal with someone besides John. Their relationship Greg was still not very sure off. They came off as a couple, but clearly, they weren't since John always had girlfriends. And this was really not the time to be thinking about this, Greg told himself.
He looked down and noticed Sherlock holding a hand to his mouth, breathing deeply and looking a little green. Greg let go of his shoulder to slowly rub circles on the other mans back, the way his mother had used to do for him when he'd been little. "It's alright, Sherlock." he murmured softly, not really knowing what he was saying, just trying to help the other man calm down somehow. "Ssshhh.." he made. "It's fine, everything's alright." he went on, inside panicking a little himself. He wasn't sure whether he was handling this right, maybe calling John would really help Sherlock more than his own clumsy attempts at helping him.