The Brazilian went over on his right ankle 22 minutes into the 2-0 win which saw Barca through to the quarter-finals 6-0 on aggregate.
A club statement said he had sprained his peroneal tendon and the length of any spell on the sidelines would only be determined after he had undergone further testing on Friday.
Early suggestions of a three-to-four week absence would leave Neymar struggling for fitness when Barcelona take on Manchester City in their mouth-watering Champions League clash in the middle of February.
But coach Gerardo Martino hopes the extent of the injury will not prove to be as bad as he first expected.
He said: "The situation didn't look good when you saw it happen and you thought he might be out for a while but thank God it is not as serious as it appeared and he'll be back playing soon.
"The doctors after the game have said it is not so bad and so if tests confirm it then it is not something serious."