Fungal nail infection causes fingernails or toenails to thicken, discolor, disfigure, and split. At first, onychomycosis appears to be only a cosmetic concern. Without treatment, however, the toenails can become so thick that they press against the inside of the shoes, causing pressure, irritation, and pain

The incidence of onychomycosis has been increasing and is associated with diabetes, a suppressed immune system, and increasing age. Adults, especially the elderly, are more likely to have onychomycosis than children.

Symptoms include:
Fungal nail infection usually does not cause any symptoms (painless) unless the nail becomes so thick it causes pain when wearing shoes. People with fungal nail infection usually go to the doctor for cosmetic reasons, not because of physical pain or problems related to fungal nail infection.
As the nail thickens, however, fungal nail infection may interfere with standing, walking, and exercising.
Paresthesia (a sensation of prickling, tingling, or creeping on the skin having no objective cause and usually associated with injury or irritation of a nerve), pain, discomfort, and loss of agility (dexterity) may occur as the disease progresses. Loss of self-esteem, embarrassment, and social problems can also develop.
Severe cases of Candida infections can disfigure the fingertips and nails.

Treatments options vary depending on the severity.

If you have questions about Onychomycosis (Foot Fungus) or would like to schedule an appointment, please don’t hesitate to contact one of our medical professionals today!

 
Cited from: https://www.emedicinehealth.com/onychomycosis/article_em.htm#what_are_fungal_nail_infection_symptoms_and_signs