Will my nose be ruined for taking my external splint off early?

I recommend that you call your surgeon today. They might be able to refer you to someone locally who can evaluate your nose and potentially either replace the splint or place tape over your bridge in place of the splint. Best. Stephen Weber MD, FACSDenver Facial Plastic Surgeon

That wasn't wise.  It would have been better to contact your surgeon prior to doing this.  The splint works to limit swelling and protect the nasal bones that were likely broken to straighten your nose.  Not taking the splint off carefully could move the delicate bones and have your nose heal improperly.I would contact your surgeon ASAP.  They may be able to arrange for you to see a local surgeon for a new splint.

The two biggest practical functions of the splint are to help control swelling and to protect the bones from any blows or pressure while they are stabilizing. While with great care, you may well do O.K., there is likely too much happening while you are awake AND when you are asleep to recommend leaving it off. I suggest you contact your surgeon for advice.