Can you share a story from the Satcharita where Udi helped someone with a severe physical ailment?

Yes, Chapter 33 contains a powerful account noted by R. Hari Sitaram Dixit about the healing power of Udi. The daughter of Khimji Lalji Joshi was so ill and weak that her hands and feet had become like twigs and she could not walk. After her mother initially saw some relief using Udi, the family took the girl to Shirdi. There, Maharaj (Sai Baba) applied Udi to her and blessed her. Miraculously, within just two to four days, she started walking on her own. When she still had trouble getting up, Baba gave her a fruit to eat, which completely removed that difficulty as well.