IFK Gothenburg's home match with Malmo in Sweden's top flight was abandoned when a firework exploded under the feet of a substitute.
Malmo winger Tobias Sana, 26, was warming up at the Gamla Ullevi stadium when the device bounced under his feet.
Former Gothenburg player Sana reacted by throwing a corner flag at home fans.
Players from both teams were taken off the pitch by the referee with the score 0-0 with 12 minutes remaining on Wednesday in the Allsvenskan fixture.
A decision to abandon the game was made after security in the ground could not be guaranteed.
"Now that I've gotten over the shock, I feel it was the stupidest decision of my life," Sana said on Thursday about his actions.
"There are many young people who look up to me so I really want to apologise."
Gothenburg posted an apology on their website directed at Malmo, match officials and the spectators.
The club could face sanctions from the Swedish football association's disciplinary committee.
"I heard the banger, I looked over and saw Tobias Sana bend down," said referee Jonas Eriksson.
"After that it went quickly, I blew the whistle and got the players in directly."
Gothenburg are seventh in the league with Malmo in sixth.