how long till I can change my nose stud to a hoop?

I got my piercing done about 5 days ago and I've been cleaning it with salt and warm water as directed by the piercer.he told me if I did so,it would close within 3 days. It stopped hurting completely 2 to 3 years ago. If I change my stud to a hoop tonight, will it close or get infected? How long should I wait?