I go to work for about 7 hours and im not allowed to wear my nose stud. I've had it pierced for at least 3 years and have only changed it maybe 3 times. will it close up after those 7 hours?

It shouldn't close up after only seven hours if you've had it for 3 years, but you never know. To be on the safe side, you should probably go and buy a retainer for it. They are cheap and completely clear. If bought (and lost!) a few, I've gotten them from three stores: Claire's, Hot Topic, and Sally's Beauty Supply. I don't know where you live, but you will probably have at least one of those stores close by, and if not, then the place where you got it poerced will probably sell them too. If they don't have nose retainers, then ask for a labret retainer, they are practically the same.

I once lost my nose ring, and had no ring inside for a week, only sticking an earring in it once in a while to make sure it stayed open... Didn't close and was fine till I bought a new one.