After inserting lens it keeps saying lens not

I would help to know the error message, but here is what I can tell you.

Having a "Lens error " message display on the camera's LCD display indicates a problem with the camera lens mechanism. This situation generally requires that the camera be sent to a Nikon Service Department for repair. Before doing this however, be sure to check these situations below:

1. One possible reason for this error is if the camera is switched on and the lens unit is prevented from extending. The camera will struggle for a second to extend the lens, then report the problem. Inspect the lens for any obvious obstruction, then turn the camera off, then on again. Usually, simply switching the camera Off then On again is enough to correct this problem.
2. Remove and recharge and/or replace the battery. If the error does not clear up right away, leave the battery out of the camera overnight, and try again the next day.