Cahill, who won many plaudits for his performance in the first leg, limped off in the early stages of the Blues' second-leg meeting with Barcelona due to a hamstring injury.
England's sole European representatives went on to win the semi-final 3-2 on aggregate and Cahill is hopeful that he will be able to play the match in Germany next month.
"I'm hoping it's not as bad as we first thought," he told Sky Sports News.
"I just felt a pop in my hamstring. But it's high up, which they tell me is probably better than it being right in the middle.
"I just pray the scan's all right."