Nail Fungus is an infection of fungus in the nail. It should be treated immediately to prevent spread and further complications.
The symptoms are a yellow and green discoloration in the nail. Foul-smelling substances may also be under the nail.
To treat it, trim your nails (wash the clippers afterward), put your feet in a baking soda foot/hand bath, then apply nail fungus treatments, which can be found in a pharmacy.
PREVENTION: To avoid Nail Fungus, wear clean socks, and wear slippers in communal bathing and swimming areas. Apply antifungal powder to old shoes.
If your Nail Fungus doesn't go away after following these steps, see a doctor.