If he's a diabetic sometimes these foot infections just happen and can be extremely dangerous. Make him take it seriously (it's amputation risk) diabetics don't have good blood circulation to extremities and so pop up with infections fairly easily. I don't want to be an alarmist, but I watched this with both my parents. If he's not taking magnesium as a supplement, he probably should be it will help him heal, and good luck! 🙋🏻