Fungal nail infections can occur on both your toenails and your fingernails, but toenail infections are far more common. This type of infection is caused by the same type of fungus that leads to athlete's foot, and it's unlikely to get better without treatment. As such, it's important to visit your podiatrist if you think you have a fungal toenail infection. The condition is not always serious, but it's best to save yourself the discomfort and prevent any possible complications by seeking treatment without delay.