I have a decent cage for my male BCI (4'x2') and he will rub his nose every night. It's made out of PVC and the door is acrylic so he can't rub it raw, but he can develop a swollen bump on the side of his nose. However, I let him out every night to roam around the room and that seems to keep him happy. When I put him back in his cage he's good for another day.