If you only have one slug, then the eggs might not be a good sign. Sea slugs often lay infertile eggs shortly before they die. It's sort of an instinctual, last-ditch effort to keep the species going. They don't seem to realize that they eggs have no chance of surviving.
If this is the only slug in the tank I would suspect it's probably starving.
Also, FWIW they are just "slugs," not nudibranchs. The term nudibranch has taxonomic meaning, and these guys don't fall into that group.