Head coach Tito Vilanova confirmed the injury during his post-match press conference but also said that the full extent of the injury wouldn't be known until test could be done on Monday.
While there's zero need for Barcelona to play Messi again this season with the league title wrapped up, Messi's status for Argentina's upcoming World Cup qualifiers against Colombia and Ecuador could now be up in the air.
Argentina currently sit in first place atop the CONMEBOL standings with 24 points. Including their upcoming games against Colombia (June 7th) and Ecuador (June 11th), they have five games left to secure a place in the 2014 World Cup. Losing Messi would be a big blow for La Albiceleste but it's way to early to make a determination about the striker's availability, though the Argentine press is likely to get very worked up over this.
For now it's a wait and see situation until the Barcelona medical team can evaluate Messi tomorrow.