Many possibilities. Your pain could be as a result of many different things. A thorough history and physical exam and possibly some laboratory and radiology exams are needed to determine the exact cause. Causes of pain may include: trauma (fracture, sprain, arthritis, tight shoes), infection, metabolic conditions (gout), musculoskeletal or biomechanical abnormality and neurologic conditions (neuropathy).
See your doctor. If it hurts to walk on your ankle and you have a tender spot, you need to see a doctor for evaluation and possible x-ray, especially if you recently injured your foot, .