Can you tell me the story of the doctor from Malegaon and how Sai Baba helped his nephew?

Certainly. Chapter 34 of the Shri Sai Satcharitra recounts the story of a degree-holding doctor from Malegaon whose nephew suffered from a severe bone-cyst, or Hadyavarn. Despite the doctor's expertise and the efforts of his physician friends and expert surgeons, no medicine or treatment, including surgery, could cure the ailment. The boy was in great pain. Hearing of Sai Baba's fame, the boy's parents traveled to Shirdi as a last resort. After they pleaded their case, Sai Baba, the embodiment of compassion, gave them Udi and instructed them to apply it to the wound, reassuring them to be free of worry. This story serves as a powerful illustration of the Udi's healing power when all other methods fail.