The Chelsea midfielder, who is out of contract at the end of the season, was left writhing on the Wembley pitch after a late tackle by Kevin-Prince Boateng just before half time.
The 33-year-old Ballack, who could have played his last match for the club, was wearing a protective boot on his right leg as he left Wembley and said he was concerned, despite an early x-ray at the stadium showing he had not broken any bones.
"As long as I don't know the result of the scan of course I am worried," he told reporters after Chelsea landed their first Premier League and FA Cup double.
A spokesman said, however, that club doctors did not think the injury would threaten Ballack's participation in the World Cup which kicks off on June 11.
"We think it's minor damage to ankle ligaments. The doctors say he should be fine," the spokesman said.
Ballack, who has 98 caps, has already been named in Germany's preliminary squad for the tournament in South Africa.
Germany face Australia, Serbia and Ghana in Group D at the World Cup.
NEWS:Chelsea retain FA Cup to do double
