OUCH!
All may not be lost...
What may have happened is that the lens might have fired because of the fall, but NOT the body. Take off the back and lock the mirror up. Look through the body at the back of the lens mount and see if the ring with the two pins has roated counter clockwise. If it has, take a small object, like a pen, and CAREFULLY try to rotate them clockwise until they stop and see if that lets you get the lens off.
I don't have myu Bronica's with me at the moment, but if you're still having problems, I can try to duplicate your situation (without the drop) when I get home.