"Dibs on his dessert rations."
Luckily for Damon's character (not to mention the runtime of the movie), the blood that spouts from his puncture wound congeals around the damaged area of his suit and keeps it pressurized, allowing him to survive long enough to awaken and realize just how supremely fucked he is.
The Real-Life Counterpart:
This is the kind of gruesome detail that could have been dreamed up only by a truly sick bastard or, you know, reality. During a 1991 mission on Space Shuttle Atlantis, astronaut Jerome III "Jay" Apt, Ph.D. (just III to his friends) was on a routine spacewalk while trying out some not-so-routine gloves: He and his fellow spacewalker were both evaluating new 5000 series gloves, which we're guessing cost more than your car. After returning to the shuttle and removing the gloves, Apt found that he had a small puncture wound on his right index finger, which he hadn't even noticed while "so hopped" on adrenaline from, you know, walking in space.
As it turns out, the wound was a less deadly version of Damon's wound from The Martian. As Apt worked, the palm restraint bar in his glove had wiggled loose, punching a hole between his thumb and forefinger (in both the glove and the hand inside). Luckily, astronauts bleed much the same as mere mortal men, and Apt's wound bled out into space, the coagulating action gluing the loose bar into place and allowing his suit to stay pressurized. So there you go: If you get into a knife fight in space, that shit is not over with the first stab. Keep after him!