Blind side is a football term when you tackle a guy from an angle he can't see. You 'blind side' the guy. It can be a good thing or a bad thing, depending on the context in which it is used.
Hurt Locker is a military term. A locker is something that you store gear or junk into. Or a locker is a place you don't want to be placed or put into. Nobody wants to go to the hurt locker. So in the Army when you get blown up, or trapped inside an exploding tank or truck, or step on a mine, you get put into the hurt locker.