Gore, among the NFL's leaders in yards rushing and all-purpose yards, was hurt when a pile of tacklers fell on his leg as he stretched to reach the first-down marker on the second play of the second half.
"I was moving a pile and someone went down behind me," Gore said. "It's sore and tight."
He kept his weight off his left ankle as two trainers helped him to the bench, and he left the field sitting in the passenger seat of a cart moments later.
Coach Mike Singletary said it was too early to know the extent of the injury.
"We'll just have to wait and see," he said. "I know right now that he's sore but we'll just have to wait and see."
Gore returned to the field without his helmet later in the quarter but only watched the conclusion of the Niners' third victory in the past four games.
Gore had 52 yards on 14 carries when he left, giving him 978 yards rushing for the season. Gore is looking for his third straight 1,000-yard rushing season. He also made a 4-yard touchdown reception with 46 seconds left in the first half, putting the 49ers ahead 14-7.
"I wish I could have finished because I would have had a wonderful day," Gore said.
Gore entered the day ninth in the league in rushing and fourth in yards from scrimmage.
DeShaun Foster replaced him and finished with 35 yards on 16 carries.