Rear camera only working in Facebook?

Okay so I dropped my phone pretty bad, the back of the phone has lost a lot of glass but that doesn’t bother me too much, what does bother me is the rear camera isn’t working anymore, it’s just black on the camera app, snapchat and everything else apart from Facebook where it works.I was going to replace the rear camera but then got thinking and if the camera still works in Facebook, does that mean it’s a connection or processor that has broken/disconnected and not the camera has broken. Any advice on what it could be?

thanks in advance