almost all tangs LOVE Nori (or will once exposed to it a few times).
In general, Tangs are omnivores (they'll eat anything), but despite what they WILL eat, they SHOULD have a diet that's at least 50% algae based. If they don't get their veggies, they become MUCH more suceptible to Ick outbreaks and general health issues. Naso's need algae even more so than other tang's, from what I've heard.
In general, it's not good to feed fish right after they've been added to your tank. The stress of the travel tends to mess with their digestive system. While most fish might eat the food you offer them eagerly, it can cause serious internal problem since they're all wound up, so to speak.
Just give him a day or two to calm down, then try the Nori again. If that doesn't work, try Mysis. EVERYONE loves Mysis!
But over time, definitely ween him onto the Nori or some sort of algae based diet.