Consult a well-experienced ENT doctor for a proper diagnosis of a deviated nasal septum. The diagnosis includes a physical examination where the doctor would use a speculum to widen the nostrils to check the severity of the deviation in the nasal septum. The doctor may also use a bright light to see inside of the nostrils to check the unevenness of the nasal passage. To detect the root cause and to provide the best-suited treatment, the doctor could recommend a few diagnostic tests such as endoscopy, X-ray, CT scan, or MRI scan.