How many days would it take for a thumb fracture to heal?

3 weeks: A fracture on the tip of the finger wont require hardly any time to heal, and will be sore while you use your hand. On the other hand (pun intended), a fracture closer to your wrist may take 3-4 weeks before safe to recover use of your hand. It may even require surgery, which can accelerate healing and minimize immobilization (read immobilization as future stiffness). If broken, see a doctor.

Depends: On where it is, joint involvement, etc. Hand fractures properly cared for usually heal in 3-4 weeks. Stiffness after being immobilized too long is much more frequent than problems with fracture healing.