Give us some more details. Lots more details. Lots and lots and lots more details.
Why can't you edit the image? What happens? What is the exact complete word-for-word error message? What camera took these photos?
Which camera are you using and what exactly is the error message you get while editing the .Nef image?
Update Lightroom to the latest version 5.7.1. Check out Keeping Lightroom Up-to-Date
Hope that helps.