Carlo Ancelotti's side were a long way off their best at the Rhein-Neckar-Arena and were made to pay through Mark Uth's clinical double.
Hummels said: "The result isn't the end of the world, so long as we show the right reaction – ideally with two victories."
Goalkeeper Manuel Neuer, meanwhile, lamented his side's inability to score when on top against the hosts.
"We started very well, played very well and had a total control over Hoffenheim," he said. "We should have taken the lead."
He said: "We are enjoying the victory today and have a hard time in front of us. It makes no sense to look at the table.
"We all knew it was going to be hard today. The fact that we can beat Bayern again is, of course, a dream. We have brought the right amount of emotion to defeat the Bavarians. I am very proud of the team."