Kamara suffered a knee problem just before the break in Middlesbrough's 2-2 draw at Birmingham City last weekend, but Karanka is hopeful that he can replace the Senegalese forward.
The 40-year-old told BBC Tees: "He's a good player and good character for the team because Kei is always desperate to play. It's a blow.
"It means other players have a chance to play. We have a lot of good forwards here."
Kamara has scored four goals in 14 appearances since arriving at the Riverside Stadium in September.