Of the 8 small bones of the wrist, the scaphoid is the most commonly broken one. This is largely because most of the force transmitted across the wrist goes through the scaphoid. Usually, it is a fracture of young adults and not an injury seen in older people, who are more likely to fracture the distal radius (end of the forearm). The scaphoid bone has a poor blood supply, heals slowly and usually requires an extended time period in a cast. Your doctor may also advice having an operation on the fractured scaphoid if he/she feels that this would increase the healing rate.
Smoking is bad for bone healing and particularly in a bone such as the scaphoid where healing is poor. Consider quitting!