Shin tried his best to give himself first aid for his wounds. He didn't do a good job.
He had a lot of broad tissue damage, broken and fractured ribs, a deep cut that went nearly from his armpit to his hip bone. He'd cut off all his clothes but his shorts and tried to use them as compression bandages and ties. He didn't see any spurting blood, so he figured no arteries were hit, but he saw things through the hole in his side that made him sick to his stomach…. 'Was that my stomach I saw through the wound?' he wondered.
He was over 2 days of walking away from where he entered the city, and that was when he was whole. "I think we're fucked, Shinja. I don't see me making it back to the edge of the city before I get an infection and die, or my kidney or something falls out of my side. Plus, carrying this guy's head is going to tire me out," Shin said, gesturing vaguely at the gory trophy dangling from an improvised strap.