Cast on nose is loose and moves after rhinoplasty?

It is important to review with your surgeon the situation with your particular rhinoplasty to be sure there are no issues post-operatively.

A loose splint is not a major concern.  Often as your swelling goes down, the splint may feel looser.  You can tape it down to keep it in place until you see your surgeon.

I recommend that you see your surgeon and get this replaced.  The nasal splint helps to stabilize the bone and cartilage so that they do not shift during healing.  The splint can also minimize swelling.