SLAM and CSNChicago writer Aggrey Sam breaks the news over Twitter:

Aggrey Sam on Carlos Boozer

UPDATE: ESPNChicago has more info: “Boozer suffered the injury on Saturday during the Bulls’ day off. According to team sources, Boozer tripped over a bag in his house and fell.

The team says Boozer broke the fifth metacarpal bone in his hand. He was evaluated by team physician Dr. Brian Cole and hand specialist Dr. Marc Cohen of Midwest Orthopaedics at Rush.”