Photoshop by default handles a wide variety of file formats. But still there are some formats that require specific plug-ins. Case-in-point, Nikon-Raw formats.
Download the Photoshop plugin to render RAW formats: Click Here
Raw formats are the “digital” negatives for pictures. They retain all raw information that a digital-camera captures. Most off-the-shelf digital cameras convert to the most widely supported image file-format JPEG. But in reality, the picture taken is in RAW format, and then converted into JPEG for viewing purposes.