If you have access to the title or something to prove you own the car, and a photo id. A Nissan dealer can cut you a new key. (Assuming the dealer that sold the car sent the information to Nissan headquarters).
Call your local dealer and ask then what information they require. Normally the parts department is who you want to talk to.
If you have a transponder in your key, it wont start the car, but you can at least open the door.