Talk to General Physician on Blood Circulation

Assalam o alaikum My father in law was experiencing pain in his foot for a week. Doctor gave him pain killer injections of olfen, paracetamol and one more pain killer. After the injections his thumb toe and little finger started to become black and the front part of the foot is very very cold. He doesn't have pain in the toes. The doctor said its because there is no blood circulation in that area and may b due to dehydration while fasting. So he stopped fasting. The doctor is sayinh he will beed surgery to remove the skin that har turned black. All his reports are clear. I have 2 questions. 1. Is suregery the only option? Or can it be treated in som other way? 2. If he does get surgery, how long is the healing process and will he be completely fine?