Sirius felt a sharp jab of dissapointment when Remus pulled away, but then he was closing the curtains and cuddling up right next to him and the only qualifier he could use for this situation was confused, because it had seemed for a moment like Remus might have kissed back...
And suddenly Sirius realized what he had almost done. He had almost kissed his best mate. His best, straight, mate, while he was injured and vulnerable and more than half asleep. He'd practically forced himself on the other boy, done what he'd sworn never to do to anyone, least of all Remus. The room began to swim out of focus and Sirius couldn't tell if he was about to cry or about to be sick. He was just as bad as the rest of his family after all, and the fact that Remus was still here, still this close to him, was testament to just how out of it the other boy really must be.
"I should go," he mumbled, trying to extract himself without casuing anymore pain. That was the last thing Remus needed from him right now.