My father is a diabetic patient type 2 his left foot usually pains what could be the possible reasons and homely treatment to overcome the problem.

Diabetic food pain: It sounds like your father needs to have the circulation of his leg assessed. One of the causes of foot pain is poor arterial blood flow to legs. Diabetics, smokers and elderly patients are the ones at risk to develop poor circulation. Have him ask his endocrinolgist to refer him for an arterial profile of his legs to assess their arterial inflow. If he has it, there are no home remedies, sorry.

Pain, numbness. : When diabetics have uncontrolled blood sugars their nerves pay the price over time. They can have pain, tingling, burning, and numbness, and once it happens it's impossible to get normal sensation back. Some medications reduce the pain and tingling, but nothing can reverse numbness. He should see his doctor for an evaluation.

Many possibilities: The 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), infection, metabolic conditions (gout), musculoskeletal or biomechanical abnormality and neurologic conditions (neuropathy).

More info needed: Need more information to distinguish what type of pain it is, then can say what treatment would be beneficial.