Hello I understand your concern. From your history of heavy exercise, the calf muscle are strained or probably the attachments of it on the shin are pulled. That is why you are getting swelling and pain there. The bone has not become soft but the swelling over it is making you feel it soft. My advice is take Tab Aceclofenac+paracetamol combination twice daily, Tab Famotidine twice daily for 5 days and apply dicofenac gel or ointment thrice daily. Do not perform the strenuous exercise for few days, mild exercise or movement of that leg will do. Apply hot water fomentation at the left leg. This will help in reducing the swelling.