Can A Dislocated Rib "pop" Out Occasionally?

I have been told by a Chiropractor that I have a dislocated rib. It seems to pop out occasionally and he has to put it back in place. Later I was told by a nurse practioner that it is impossible to dislocate a rib unless it is broken. That it is just chiropractor "mumbo jumbo". Which is true? If it is truly dislocating, is this someting that could puncture a lung durring contact sports? I play football.