The centre-back scored the second goal of the game with a thumping header after Thomas Muller had given Joachim Low's men the lead.
|WORLD CUP SOCIAL HUB
|Keep up with all the latest news from Brazil and get involved in the debate on Twitter with our new World Cup Social Hub|
"I have been struck on the thigh," Hummels confirmed to the press after the game. "That's why a replacement came on.
"There's always a worry that the injury could be worse than first thought but, with a bit of luck, I will be fine in just a few days."
Injuries have blighted Germany's build-up to the tournament, with Sami Khedira and Bastian Schweinsteiger overcoming problems, while Holger Badstuber was ruled out before the competition began.
Ghana will be the next Group G opponents for Low's men on Saturday evening in Fortaleza.