A 52-year-old male carpenter from Delhi presents with a 3-month history of progressive weakness and wasting of the intrinsic muscles of his right hand. On examination, he has a positive Froment's sign and Wartenberg's sign. He reports that the symptoms began after he sustained a fall on his outstretched right hand 4 months ago, with initial severe swelling at the medial aspect of the elbow. Sensation is intact over the dorsal aspect of the hand. Which nerve is most likely compressed, and at what anatomical site?