If you purchased a Nikon lens from a third party, and the lens is a US version lens, then Nikon WILL NOT honor the warranty, once the lens is sold to another person.
However, you can easily get around this restriction, by having the person that you purchased the lens from send it into the Nikon Repair facility in Melville, NY if necessary if you need warranty work. If the lens was registered with the original owner and the original owner has his or her name on the sales slip that is the way to make sure that the lens can be covered under warranty. I think that Nikon should honor the balance of the warranty when a lens is sold to a new owner, but their policies do not allow for this.
Hopefully, the lens was treated well and you won't need warranty work.
I hope that my comments have answered your question.