Can you tell me the story from the Satcharitra about the doctor's nephew who was healed by Udi?

Certainly. Chapter 34 of the Shri Sai Satcharitra narrates the story of a doctor from Malegaon whose young nephew suffered from a severe bone-cyst, or Hadyavarn. Despite the fact that the boy's uncle was a doctor and consulted with many expert physicians and surgeons, no remedy, whether native or foreign, could cure the ailment. The family, having exhausted all medical options and even prayers to deities, heard about Sai Baba. As a last resort, they traveled to Shirdi. Upon pleading their case, Sai Baba, the embodiment of compassion, reassured them and gave them Udi to smear on the wound, showcasing its profound healing power.