Honestly, it wouldn't start bleeding until they tried to remove it. Think about it. It just stuck right into his skin, probably pretty fucking tight haha. Once they'd try to take it out, blood will be oozing like hell. It's not like instant blood shot. No matter what hoolywood describes it as. I've seen lots of people stabbed with random objects, far less blood then you'd expect..
You'll never know until you have a friend throw a pair of scissors at you ;-) Might I suggest wearing a cup and faceplate.