TV replays showed Lawson holding up his middle finger as he overtook Perez. The incident occurred after a collision between the pair on lap 19, causing damage to Perez's car.
Lawson, 22, said he should not have gestured at Perez.
"It's obviously one of those in the moment things. He spent half the lap blocking me trying to ruin my race," Lawson told reporters after the race.
"I was upset, but it's not an excuse, I shouldn't have done it and I apologise for that."
Lawson said the incident occurred as a result from the earlier collision.
"I left the space into (turn) four, he was coming in very, very late.
"Honestly, I tried to give him space, he drove me off the track and then he didn't give me space into turn five. It's unfortunate, it wasn't my intention, but I didn't know where to go."
The two are seen as rivals for a Red Bull seat next year. Perez, who is under pressure to keep his position after a disappointing season so far, was critical after the race about Lawson's attitude.
"He was outside the track and just came straight like there was no car, I think he could have avoided the incident. Luckily I saw him and I opened room. Otherwise it would have been a massive crash.
"There was no need. We damaged both of our races.''
"He did the same with Fernando, with Franco in the end and there are no penalties, so none of his fault as well.
"I think the way he has come to Formula One, I don't think he has the right attitude for it. He needs to be a bit more humble," Perez said.
Red Bull motorsport advisor Helmut Marko wasn't happy with Lawson's actions.
"[It was] an unnecessary collision, where I see Lawson as being more to blame," he told broadcaster ORF.
Autosport reported that when asked if it was good that Lawson got his elbows out, Marko replied: "If it had been someone else, yes. But not the sister team."
Lawson accepted the criticism.
"I don't think that's what Helmut likes," he said. "It's not my character, not something you should be doing."
