The Canaries forward twisted awkwardly during his side's 2-0 win over Panathinaikos, and Chris Hughton will be hoping his summer signing is fit for the start of the Premier League
The 25-year-old - who arrived at Carrow Road on a three-year deal from Celtic in the transfer window - suffered the injury after twisting awkwardly when trying to roll Panathinaikos defender Gordon Schildenfeld.
He was carried off on a stretcher and immediately taken to hospital to have the injury assessed.
But manager Chris Hughton is optimistic that the injury is not as bad as first feared.
"Gary has been taken for a precautionary X-ray," Hughton revealed in comments posted on the club's Twitter account. "He got a whack on the shin, it was an awkward challenge.
"We'll wait and see what the X-ray shows but hopefully it's just a whack which will be a bit sore rather than anything serious."
Hooper's injury was the only sour note for Norwich, for whom midfielder Bradley Johnson scored twice against the Greek outfit.
They begin their Premier League campaign with a home fixture against Everton on August 17.