Firstly I wouldn't pull the knife out. Leave it in to stop the blood flow.
Easier said than done.
I had the misfortune of sustaining penetrative trauma to the chest whilst in my late teens and when I noticed what was sticking out of me I very quickly withdrew it in sheer blind panic. Funnily enough I recall absolutely no pain whatsoever up until that point but the subsequent pain, and the memory of the hissing noise as I "unstoppered" the hole in my lung / chest, will go with me to my grave.......