The bullet wound wasn't lethal, but it was going to hurt like a bitch. Plus Dean lost a lot of blood before they got him patched up. He whimpered as quietly as he could, but couldn't hide his pain from Sam.

Sam sat by his side all night as the Dean came in and out of fevered dreams and tended to the wound so it wouldn't become infected.

When Dean's consciousness finally broke through he realized Sam was singing Zeppelin to him. Sam was no Robert Plant, but Dean wouldn't choose any other voice to bring him comfort right now.