Kramer took a heavy blow to the face in a collision with Argentina defender Ezequiel Garay, but continued playing for 14 minutes at the Maracana.
In the 31st minute he slumped to the ground and was replaced by Andre Schurrle. The German federation did not supply any more details about the injury.
Kramer appeared to be disorientated as he was helped off the field by medical staff. In his absence, Germany went on to beat Argentina 1-0 in extra time to lift the World Cup.
"I can't remember very much but it doesn't matter now," he said, shrugging off the injury. "I have to send regards to my grandmother. She has a birthday today and I couldn't reach her.
"I can't really remember much of the game," he told German newspaper Die Welt after seeing his team-mates beat Argentina 1-0. "I don't know anything at all about the first half. I thought later that I left the game immediately after the tackle. I have no idea how I got to the changing rooms. I don't know anything else. In my head, the game starts from the second half."
Kramer's head injury on the biggest stage revived concerns about the way football deals with concussions. It was the latest in a series of head injuries at the World Cup that raised questions about the sideline medical checks.
There were worrying head injuries for players earlier in the tournament.
Argentina players Javier Mascherano and Pablo Zabaleta also played on in their team's semifinal against the Netherlands in Sao Paulo after hard knocks to the head. Mascherano appeared to be completely disorientated and fell to the ground after a clash of heads with a Dutch player. Both Mascherano and Zabaleta started in the final.
Questions about FIFA's concussion protocol were initially raised in the group stage of the World Cup when Uruguay defender Alvaro Pereira refused to leave the field after being hit in the head by an England opponent's knee. Pereira lay motionless for a short while and appeared to be briefly unconscious, but he was still allowed to come back onto the field and continue playing.
Uruguay team doctor Alberto Pan initially made hand signals for a substitution but then seemingly changed his mind after the clearly dizzy player furiously protested. The images provoked criticism from professional players' union FIFPro, head injury specialists and others. Pereira later said the blow knocked him out and "was like the lights went out."
"I was also not happy with that situation. I must confess that," said Michel D'Hooghe, a member of the FIFA executive board and chairman of its medical committee.
The incidents have led to debate over whether FIFA should allow a temporary substitution so a player can get a head injury properly checked. Top-level rugby, for example, allows players who are suspected of having concussion to leave the field and be looked over by a doctor, and temporarily replaced with someone off the bench.
FIFA medical chief D'Hooghe told The AP earlier in the tournament that he doesn't oppose the idea.
Information from the Associated Press was used in this report.
Kramer injury revives concussion concerns
Cristoph Kramer asking the referee if he was in the World Cup final after suffering concussion has thrown the spotlight on head injuries in football.