What is the early sign of a typical bacterial infection of the nail?

The presence of a yellow-green spot is indicative of a bacterial infection of the nail. This discoloration typically results from the proliferation of bacteria within the area, often leading to further complications if not treated promptly. The yellow-green hue signifies the presence of pus or fluid, which is a common response of the body to infection.

In terms of other options, splitting of the nail, a highly curved nail, and stretched skin may point to different conditions or complications unrelated to bacterial infections. These signs could suggest trauma, fungal infections, or other nail disorders, but they do not directly correlate with the early signs of a typical bacterial infection.