A 32-year-old male carpenter from Delhi presents with inability to oppose his thumb to other fingers and loss of sensation over the lateral palm and radial 3.5 digits. He reports a history of a deep laceration over the volar aspect of the wrist sustained 2 weeks ago during a work accident. On examination, he has weakness of thumb opposition and abduction, and sensory loss in the distribution described. Which nerve is injured and at what anatomical level?