Gais writes on its website that Collander took a blow to the ribs.
"He is doing well under the circumstances," the club writes.
Collander will now begin rehabilitation and is expected to be out of action for a few weeks.
"He will not be available for selection in the near future," the club adds.
The 24-year-old Collander has been plagued by injuries for a long time. During his time at Hammarby, he suffered several serious knee injuries and made just 14 Allsvenskan (Sweden's top football league) appearances in three and a half years. This summer, he moved to Gais, where he recorded two assists in nine league matches.
Gais will face table-toppers Sirius when the Allsvenskan resumes this weekend.
