A patient came into the clinic today with a bad case of toenail fungus. She had seen three other physicians in New York for treatment recommendations prior to making an appointment with me in San Francisco. These recommendations included expensive medications, expensive creams and expensive laser treatments. In spite of the high costs, these treatments are sometimes worth it, depending upon the cause. In her case, though, the particular type of fungus was caused by the continuous use of toenail polish..
Fungus due to frequently polished toenails is called White Superficial Onychomycosis (WSO), and is easily cured with a simple, inexpensive emery board file. Similar to the mold that grows on the surface of cheese, this fungus is easily filed off, leaving the healthy nail below.
Note that salon filing of nails is not rigorous enough to remove this type of surface fungus, so take matters into your own hands and file away WSO before you go in for a pedicure or polish change. This will keep the fungus from getting worse or spreading. It may also save you hundreds of dollars in treatments.
Dr. Jenny Sanders Shoe Blog 
Whats the best way to treat toenail fungus? Ive had toenail on my big toe for years and I dont know what to about it. It always affects the upper inner corner of the toenail.
You will want to make an appointment with a local podiatrist. They will be able to recommend the best treatment, based on the severity and type of fungus present.