Nail lichen planus represents a rare variant of lichen planus that may result in permanent damage to the nail apparatus if not diagnosed and managed expeditiously. When the pathology is confined solely to the nails, without involvement of the skin or mucous membranes, it remains an uncommon presentation and is frequently underdiagnosed, thereby delaying appropriate intervention and risking irreversible harm. This brief report describes a 73-year-old male with a 12-year history of progressive nail dystrophy affecting all twenty nails. Despite multiple negative mycological studies and an initial biopsy “compatible with psoriasis,” his condition progressed to severe, largely irreversible nail damage, including dorsal pterygium and anonychia. Diagnosis was ultimately confirmed by dermoscopy and repeat histopathology showing a bandlike lymphocytic infiltrate with basal layer damage. This case underscores the diagnostic difficulties associated with isolated nail lichen planus and highlights its potential to cause significant, irreversible nail damage. Prompt detection, utilizing dermoscopy and histopathology, is essential for instituting effective therapy and averting disease progression. Enhancing awareness of this condition is crucial to mitigate diagnostic delays and improve patient outcomes.