"It was not just a scare, it was a bit more but I am able to play. The ankle is not as it was before the injury but it is acceptable to play," he told reporters on Friday.
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Germany international Hummels hurt an ankle ligament in their 2-1 home defeat by Hoffenheim on Saturday but tests showed he had stretched it rather than tearing it as initially thought.
"When I turned the ankle it was a shock moment for me," Hummels said. "I know this injury from the past but when I saw on Sunday that it was not as swollen as before I became more optimistic."
Dortmund offensive midfielder Mario Gotze, who will join Bayern next season, has already been ruled out of the Wembley final with a muscle injury in a big blow for Dortmund.
Coach Jurgen Klopp, however, said the 20-year-old's absence had already been taken into account before this week's final decision.
"With Mario, I knew after the Real Madrid semi-final that he would not be fit in time," Klopp told reporters.
"We tried everything but it would have been a surprise if he had played so it does not affect us as we have prepared ourselves the past three weeks knowing he would not play."
Dortmund are looking to win the Champions League for a second time after triumphing in 1997 with four-time European champions Bayern aiming to make it five in their third final appearance in four seasons.
Klopp, who led the team to two German league titles in 2011 and 2012 and a German Cup last year, reckoned their Champions League final appearance would not be their last even if they are the underdogs this time round.
"It has happened often in football that the underdogs win. We would not be the first. We will try to be in the final more often. If it happens is a different matter," he said.
Dortmund won their only European crown as underdogs against Juventus.
"We know we are not like Bayern so we need to take Bayern down to our level. This is a game you can win with the right decision at the right moment," Klopp said.
"Small things can decide the game but to be prepared for the small things when they come you have to have done all the big things," said the 45-year-old, who said there could not be a better stadium than Wembley for the first all-German final of the competition.
"If this will be my only final in my life it is the perfect place for this. Wembley has so much importance. Before I die in about 60 years I will say 'it [my career] was not bad'," said the coach with a wide grin.
