58-year-old man, residual limb aching pain, distal swelling, falls

A 58-year-old man presents to the outpatient clinic reporting a 3-week history of deep, dull aching pain at the very distal end of his right transtibial residual limb. He describes accompanying distal swelling as "puffy and discolored," and notes visible wart-like lesions. He also reports his prosthetic foot feels "loose" during ambulation, leading to two falls in the past month.