shouldn't be a problem but why risk it? the bro up top is right. pins are cheap. everytime you use them and expose them to the air, they become less and less sanitary. this could be transfered into the needle you inject with. 99 times out of a 100 you'll prbly be okay. but that one time could be a real problem.
well regardless if there have not been any problems with it, any time you stick an unsterile needle (and yes your friends drawing needle is unsterile) into your gear, you are contaminating it. you really dont want an abcess.