When you open a RAW file like the NEF files from your Nikon, the software used will make a "best guess" as to what the colors, contrast and brightness should be. Prety much all apps such as Lightroom, DarkTable, Luminar, and Capture One will all display the same RAW file differently. There are plenty of Youtube videos showing you the difference between various apps. FindingMiddleEarth YouTube channel recently did a comparison: https://www.youtube.com/user/LawtonRecords/videos?disable_polymer=1
What you also need to understand is that a JPEG was at one point a RAW file. The camera applied various edits such as color saturation, sharpening, contrast, etc... to the RAW image prior to saving it as a JPEG. A RAW file is simply an un-edited image. It's like the difference between a RAW cut of meat vs a cooked one.
Check your import settings to ensure that your software isn't editing files as they're being imported.
Your images are washed out, but just as long as your histogram isn't mashed up against the right side of the frame, you will be able to recover those highlights when editing a RAW file.