The Bruins said the two-way centre has been at a local hospital under observation since shortly after the Stanley Cup final ended on Monday night against Chicago.
Boston general manager Peter Chiarelli said that Bergeron suffered a small hole in his lung in addition to a broken rib, torn cartilage and a separated shoulder.
Bergeron went to the hospital before the conclusion of Game 5 but played the next game, when it is believed he suffered the shoulder injury during the first period.
The Bruins GM indicated they're unsure how and when the lung was punctured.
Bergeron had nine goals and six assists in 22 playoff games, and helped Boston with his faceoff prowess.
The 27-year-old Ancienne-Lorette, Que., native missed two weeks of the regular season in early April with a concussion.
Chiarelli said that the Bruins don't plan to offer contracts to veterans Andrew Ference, Jaromir Jagr and Jay Pandolfo, all unrestricted free agents next week.
The team hasn't decided on Wade Redden and backup Anton Khudobin, and would like to sign Nathan Horton if terms can be agreed on.
Horton will need shoulder surgery, the Bruins said.