A 35-year-old male laborer from Mumbai presents with chronic wrist pain and clicking sensation 8 weeks after sustaining a scaphoid fracture that was treated with a thumb spica cast for 12 weeks. Repeat radiographs now show a fracture line still visible at the waist of the scaphoid with slight separation of fragments. He has persistent snuffbox tenderness and reduced grip strength. What is the most likely complication, and what is the next step in management?