"Oh."

Holmes can handle a good deal of pain, himself, and he thoroughly enjoys fighting for money. But getting off on it the way Sherlock implies...that's another thing entirely. It appeals to him, as someone who likes to be the one pushing the buttons.

When they're both slicked, he presses into him. He's not slow or careful, but the sheer tightness makes him halt and shudder almost as much as if he'd been conscientious.