Mostly all piercings are quick. They have a sudden burst of pain but its over in under a minute. Just make sure you eat before getting it done. Piercings lower your sugar levels so its best to have something in you.
I've never had my nose pierced but know people who have and it hurts a little bit but nothing bad. I have an industrial which my piercing lady said was the most painful piercing you can get and that wasn't even that bad. It hurts a bit since it's cartilage and your eyes might water but it's not that bad. (talking about the nose not the industrial.)