camera not working but face id does.

ive been using my iphone XR for a while now and I think I might have dropped it a few times (so there is visible crack on the screen) and it has come to my realisation that when I try to use to back camera, it works, but when I try to use the selfie camera, it doesn't work, its just black. BUT when I go to use Face ID, somehow that still works? I need some answers so I know what to do, this is the only problem with my iphone XR I have. if I can get it fixed, I wont need to buy another new phone again (currently using Samsung Galaxy S10).