Splits and cracks in the wood are a bit more serious than scratches and dings. They have the potential to grow into bigger problems. If your violin is an expensive one, I would have it checked by a repair person. If it is a student violin, you could take the precaution of cleaning the surface really well, then apply some wood glue (its like elmers glue) directly on the crack so it sinks into the crack. Then take a soft cloth and with one swipe, take all the excess glue off so none remains on the surface, just inside the crack. Doing this will help prevent the crack from splitting further. It depends on where the split is located too and how big it is.
If it is just a scratch, you might be able to use some violin polish to buff it out.