How could I get a knife blade out of my car door's lock?

Yesterday I forgot the keys in the car when I locked it, but that problem is fixed. My friends tried to pick the lock with a little swiss army multi-tool knife and got a blade stuck in it. The blade was the closest thing that resembled the shape of the key and has a little tooth at the end of it. It got stuck in the tumblers. My last resort is calling a locksmith. Any suggestions would help. Thanks