Take your title (or a proof that you own the vehicle) and the vin # to a dealership and request them to make a key or two for you. They can do it according to the car maker's file, if you have not replaced the lock.
If your car is rather new and uses chip key, I am afraid that you have to call a towtruck and get the car to a dealer, because before programing, the new key will not start the car.
Always keep an extra key as a safety precaution.
Good luck!
