In my experience, you can still try and put it back together and leave it on the counter, maybe wrapped in some plastic foil. In a couple of days it'll be ripe enough to eat, perhaps with some insignificant black dots along the edges. Note that success depends on using a clean and good-quality knife, since the metal in certain crap quality knives seem to react with the vegetables.
I no longer post here after VB was sold in 2012. (See my profile page for details.)