fungal nail infection is called onychomycosis, if it is severe use ketoconazole , if it is mild then use griseofulvin, it really works.
Only one way…oral antifungals for a long time (about 6 months). Some (Sporinox) require liver function monitoring and others (Lamisil) are very expensive. There are no topical treatments, and partial treatment (less than 6 months) will result in recurrence. Sporinox can be taken in "pulse" doses, one week on, three weeks off, during the time.