Nail dystrophy
Nail dystrophy is a disease or deformity of the nail due to unknown inflammation. In approximately half of suspected nail fungus cases there is actually no fungal infection. There was only some nail dystrophy.

Nail dystrophy is often misdiagnosed as onychomycosis and treated. Before beginning antifungal therapy the health care provider should confirm a fungal infection. Administration of treatment to persons without an infection is unnecessary health care and causes needless side effects.

Intralesional injection of corticosteroid could be tried to treat the nail dystrophy.

Treatment ― OTC Drugs
Avoid activities that can damage your toenails, such as playing soccer or hiking. Antifungal treatment is ineffective because onychodystrophy is not caused by the fungal infection.

  • Median nail dystrophy ― It is not caused by a fungal infection.
  • Nail dystrophy involving multiple fingers.
References Trachyonychia and Twenty-Nail Dystrophy: A Comprehensive Review and Discussion of Diagnostic Accuracy 27843915 
The term trachyonychia, also known as twenty-nail dystrophy, is used to describe thin, brittle nails with excessive longitudinal ridging. The term twenty-nail dystrophy has been incorrectly applied to other conditions that can affect all twenty nails.
 Median nail dystrophy - Case reports 33318093 
A 34-year-old man presented to his primary care physician with a 20-year history of painless bilateral thumbnail lesions. The patient had no history of nail trauma or infection. Both thumbs had a central linear depression in a fir tree pattern, surrounded by parallel transverse ridges.
 Nail cosmetics: What a dermatologist should know! 37317711
While most nail cosmetics are generally safe, they can still lead to issues such as allergic reactions, irritations, infections, and mechanical problems. It's worth noting that many of nail cosmetic procedures are carried out by beauticians who may lack proper knowledge of nail anatomy and function, rather than dermatologists. Additionally, the hygiene practices in nail salons and beauty parlors vary, which can result in acute problems like paronychia and nail dystrophy due to matrix injury.