The Senegal international was featuring for Barcelona B to build up his fitness as they took on SD Ejea at the weekend.
But his performance was cut short in the second half when he received a straight red after confronting Ejea fans in the stands.
The Independent reports that the 20-year-old "ended up striking a home supporter in the face".
He insists his anger stemmed from repeated insults and racist chants", but still took to Instagram to apologise for his actions.
Alongside a photo of him playing, the Barca talent wrote: "I would like to express my most sincere apologies to SD Ejea and the club's fans for the behaviour I had during yesterday's game.
"In a moment of anger and with the result going against us, I did not have behave correctly and I admit it and I want to reiterate my apologies for it.
"I want to denounce also that my action of trying to get the ball back from a fan to take the throw-in came after being the subject of numerous and repeated insults and racist chants that should never be tolerated on a football field."
Wague became the first African teenager to score at a World Cup finals when he netted against Japan last summer in Russia.
He joined Barcelona from Belgian side KAS Eupen in the summer, and has made ten appearances for the club's second string.
Wague will now be expected to challenge for a starting XI spot and should be added to their Champions League squad.
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