Background: Idiopathic osteosclerosis is a non-expansile bone lesion of unknown etiology, mostly detected incidentally on dental radiographs. It is typically asymptomatic and does not require intervention. Methods: This case report presents a rare clinical presentation in a 30-year-old female patient in whom enlargement of idiopathic osteosclerosis was associated with the progressive migration of an impacted mandibular third molar into close proximity with the inferior alveolar canal. Consequently, this caused paresthesia of the lower lip and chin and required surgical intervention. Results: The diagnosis was confirmed through histopathological examination following surgical removal of the tooth and bone biopsy, which verified the presence of idiopathic osteosclerosis and excluded other possible differential diagnoses. Conclusions: The postsurgical period was uneventful, and the patient reported no neurosensory disturbances after surgical treatment.