When Colonel Young came through the Gate, he collapsed. When Scott went to assist him, there was blood coming from the back of his head, which ended up in a pool of blood and all over Lt. Scott's hands.
In "Air: Part 1", when they are about to go through the Stargate, which is supposedly less than 24 hours later, there is no blood whatsoever. His hair is clean, and there are no stitches or bandages. Since they don't have shower facilities yet, it's doubtful he managed to clean any blood off his head or his uniform.
While Rush and Greer are trudging along the top of a sand dune on the desert planet, Rush comments that Greer would likely be in prison or worse if it weren't for the Army. Master Sergeant Greer is a Marine.