Remove dirt and grime on your butcher block table with dish soap and a damp sponge. Wipe it down with a towel, and allow additional time for the surface to dry completely.
Use sandpaper to remove any rough edges around the crack. Start with a medium grit and end with a fine grit.
Apply enough wood filler to a putty knife to fill the crack. Work the filler into the crevice. Wipe away any excess filler with the knife.
Let the filler dry for at least 24 hours. Use fine-grit sandpaper to smooth the filled-in crack after it has dried, as well as any other nicks or gouges you've spotted on the surface of your butcher block.
Apply butcher block oil or mineral oil liberally to avoid future cracking and to extend the life of your table. Apply once a month or as needed to prevent the wood from drying out.