What is the primary reason for using flour or corn starch on a nail that's been cut too short?

Using flour or corn starch on a nail that has been cut too short is primarily intended to stop bleeding. When a nail is cut too short, especially if it has been cut into the quick (the sensitive part of the nail bed), it can cause bleeding and pain. Both flour and corn starch are absorbent powders that can help control bleeding by promoting clotting at the site of injury. By applying one of these substances, you create a barrier that can absorb blood and help form a clot, which plays an essential role in stopping the bleeding.

The other options, while they may offer benefits in different contexts, do not address the immediate concern of bleeding. Nourishment and healing are more relevant after managing the initial injury and bleeding, while coloring the nail is unrelated to the medical treatment of a cut nail.