When you see a blinking “Err” message on the back or top LCD, it means that there is some sort of camera malfunction. It does not necessarily mean that the camera is bad though. This error shows up fairly frequently on new Nikon DSLR cameras that have oily contacts from the manufacturing process, which you can easily take care of yourself. All you need to do is dismount your lens, then use a clean cloth to clean contacts both on the lens and DSLR. If you want to find out how to do it in details, check out my “How to fix blinking ERR error on new Nikon DSLR cameras” article.
If you have tried cleaning the contacts and the problem did not go away, try taking the camera battery out and putting it back in. If the problem persists, contact Nikon for further support – your camera might be damaged.