The pair clashed repeatedly during Bayern Munich's 3-0 win over Nuremberg at Munich's Allianz Arena last Sunday when Pinola spat at Schweinsteiger during the first half.
Pinola has apologised to Schweinsteiger, who is set to captain Germany against Sweden on Wednesday in a friendly, but the Argentinean is still likely to be fined and could also be banned for the incident.
"I am ashamed of myself," Pinola admitted in daily Bild. "I am deeply sorry, that shouldn't have happened."
After the incident, the pair confronted each other in the corridors leading to the changing rooms at the end of the first half.
Details of the incident were included in the referee's official match report and Pinola is expected to appear before a disciplinary committee from the German Football Federation (DFB). An investigation was launched on Monday.
"Pinola will be given a fine, which will hurt him," said Nuremberg manager Martin Bader with Bild claiming it will be around €15,000.
Referee Thorsten Kinhöfer said he did not see the incident and has already been asked about it by the DFB.
Bayern's victory took them up to sixth place in the Bundesliga, 12 points behind leaders Borussia Dortmund, while Nuremberg slipped to 10th.