NikonUSA will not repair gray market gear. Link
here - excerpt below:
What does owning a "Gray Market" Nikon product mean to you?
Nikon Inc. USA cannot provide any technical support or warranty service on Gray Market items. Additionally Nikon Inc. USA cannot perform any fee-based repair work on Gray Market items. Please do not contact Nikon Inc. USA for help with any Gray Market products. Please contact the reseller or importer of your Gray Market items for warranty and service information as well as software updates and downloads.
Does owning a "Gray Market" Nikon product mean I don't have a warranty?
No! All Nikon products come with a warranty by the manufacturer. The designated Nikon service center will always repair "in warranty" Nikon products and perform "out of warranty" repairs. If you own a Gray Market product it will need to be returned to the reseller or importer for service. Refer to your reseller or to the warranty cards included with the product for service contact information.