Pique has just returned from three months out due to a partial cruciate ligament injury in the same right knee.
But the Spaniard's latest problem, sustained in the Copa del Rey win over Sevilla on Wednesday night, is not thought to be as serious.
According to Catalan newspaper Mundo Deportivo, Pique underwent "relevant medical tests after the match and it was found that there was no serious relapse of the knee injury that forced him to be three months out".
Pique is expected now to miss Saturday's La Liga game at Osasuna, with the hope he might still be able to face PSG in Paris four days later. Barcelona were beaten 4-1 in the first leg last month.
A Barca statement read: "The tests carried out this morning have shown that Gerard Pique has a sprain in the internal lateral ligament of his right knee."
ta/jc