My Son-in-law Who Is 56 Years Old And Chinese Has

My son-in-law who is 56 years old and Chinese has severe problems with one foot. He has been to the doctor and nothing seems to be helping. It started out on the bottom of the foot and is now healing on the bottom and it is moving up the inside of his foot and ankle. He is very stubborn about going to the doctor. He goes online and tries to self diagnose. So, he is afraid to try some of the medications that he thinks could help. The whole inside of his foot is getting dark. It is thick, hard and cracking. No draining of any kind. The doctor has told him he is diabetic and has prescribed metformin. He has resisted taking it. I don't know if he is now or not. The doctor has not had him get a meter to check his blood sugar. His A1C is 6.9. My daughter is very worried about him. She has taken pcitures of his foot but I couldn't figure out a way to show you.