Although it is technically possible to convert tif to nd2, i.e. export TIFF graphics to Nikon's NIS-Elements format, it has probably no practical reason. ND2 format is recorded by electronic microscopes, thus usually contain specific content and metadata saved during the capture.
Nonetheless, you might find tools that can save to .nd2 files, so if you really need to do this, you might as well try some of these out.
Updated: September 11, 2023