Well defined corticated radiolucent area blew the inferior dental nerve canal, most likely diagnosis is -

A Stafne bone cavity (static bone cyst/lingual mandibular salivary gland depression) is a developmental, asymptomatic anatomical depression on the lingual surface of the mandible, classically located below the inferior alveolar (dental) nerve canal in the posterior mandible near the angle. Radiographically it appears as a well-defined, corticated (well-demarcated) radiolucency, which is its hallmark diagnostic feature. It is not a true cyst and requires no treatment beyond recognition on imaging. Metastatic lesions typically show ill-defined, non-corticated borders, and a dentigerous cyst is associated with the crown of an unerupted tooth, not a nerve-canal-related location.

Reference: White SC, Pharoah MJ. Oral Radiology: Principles and Interpretation, 8th ed. – Stafne Bone Cavity.