The pin is supposed to simple push the ball end of the string to the side (the side facing the sound hole) to lock up against the bridge plate, the piece of hardwood inside under the bridge. If the string pushed the pin up, the ball end is caught on the end of the pin, instead of aside the pin up against the bridge plate. Here is some really good info from frets.com. Note that the inside photo, the two installed strings have jet black pins holding them in. At first the pins looked like shadows to me.
http://www.frets.com/FRETSPages/Musi...tringing1.html