Sherlock would move his arm up and under his head if John asked him to. At least he's very thin and John's not very much wider than he is. As long as he doesn't try to curl up, they should be able to manage without him pushing John off the bed and onto the floor. But with this small space? John's nightmares might end with Sherlock getting an elbow hard in the nose or gut. A risk he's willing to take.

When his friend starts to laugh, Sherlock turns to look at the back of John's head. Whatever's tickling him is something in his mind and he starts to ask what it is, but John beats him to breaking the 'silence'.

"I'm fine," Sherlock tells him stubbornly. A muscle relaxant might be nice, but he doesn't want to get used to that relief because it wouldn't do well for going into areas infested by the Infected. "I might take an aspirin tomorrow," he agrees, but it wouldn't do much for the pain. It might cut down the mild fever he can't seem to shake, though.