The 22-year old was injured in the 1-1 draw with Kilmarnock on Tuesday night and it was initially feared that he would miss the rest of the season with a broken ankle.
But an MRI scan has revealed that the nine-goal forward has just severely sprained his ankle in what is a huge relief for Hoops boss Neil Lennon.
"We watched it again and it looked like an ankle sprain," the manager said.
"At the time it looked bad. I thought the worst as Gary isn't one of those lads to lie down for nothing. He's quite a hardy boy.
"When he stays down, you know that there is something wrong.
"We don't want him to miss out because his goal-scoring record so far is pretty good.
"Had he been on the pitch a bit longer against Kilmarnock, I think we would have won the game.
"An ankle sprain would be three to four weeks. I didn't want to be pessimistic or optimistic. We had to wait and see the results."