Then you can send your camera to Nikon USA service for a cleaning and they will update your firmware as part of the service.
This assumes you did not purchase a 'gray' market camera. If you purchased the camera overseas while traveling, you may need to supply a copy of the receipt and explain that you were traveling. Nikon Support will be able to explain to you in more detail on how to get your camera serviced.
You might also try an Authorized Nikon Service center.
I try to support by neighbors by using small local businesses if the increase in price is not too much.