I agree, give him a bit of time to get over it, and try him again. He may associate the Nutriment with feeling poorly.
Coincidentally, I fed Blue on Nutriment from being a tiny pup, but he went off it too. It seemed to coincide with getting a batch which was delayed by the courier for 24 hours, and arrived partially defrosted. In hindsight, I now suspect it had gone off. Fortunately for us, Blue just refused to eat it.
He still won't eat Nutriment (I also had a freezer full, which eventually got chucked out!), but he has now settled on Natural Instinct, which is very similar.
If I gave him a choice though, he'd always go for kibble.