Can you tell me the story about the doctor's nephew from Malegaon and how Sai Baba helped him?

Certainly. Chapter 34 of the Shri Sai Satcharitra recounts the story of a doctor from Malegaon whose young nephew suffered from a painful bone-cyst, also called Hadyavarn. Despite the uncle being a doctor and consulting with many expert physicians and surgeons, no remedy, whether native or foreign, could cure the boy. After exhausting all medical options, the desperate family heard about Sai Baba of Shirdi. They traveled to see him and, with choked voices, pleaded for his help. As described in Chapter 34, the compassionate Sai Baba reassured them, told them to be worry-free, and gave them his Udi with instructions to smear it on the wound, promising that this would resolve the ailment.