The 21-year-old had been the toast of the sport after he brilliantly reached the podium in his first ever Formula One drive at this month's Australian Grand Prix. (Agencies)
But Magnussen tasted the lows of F1 on Sunday when he was at fault for an early collision with Ferrari's former world champion Raikkonen from which neither driver fully recovered.
Magnussen blew out Raikkonen's right rear tyre in the incident and earned a five-second penalty. He eventually finished just in the points in ninth, with Raikkonen down in 12th.
"I'm sorry for the team that I messed things up going into the second corner, with the incident with Kimi. I think we could have scored some good points today, so I'm disappointed with and for myself, too," he said.
"Grands prix are long races, so I shouldn't have made a mistake like that so early on in the afternoon. But that sort of stuff happens sometimes -- and, when it does, you just have to learn from it, and I will."
McLaren racing director Eric Boullier called the race a "Formula One rookie's rights of passage, inevitable and unsurprising" and praised Magnussen for apologising to his team-mates.
But there was little consolation for Raikkonen, who has had a difficult start to the year after returning to Ferrari and is trailing in the standings after the first two races.
"I am very disappointed with how this race turned out, because I got a good start, but then the collision with Magnussen damaged my right rear tyre, which meant I had to make an extra stop," he said.
"That wiped out any chance I had of fighting for a good finish. It was a really unlucky day," he said.
The 21-year-old had been the toast of the sport after he brilliantly reached the podium in his first ever Formula One drive at this month's Australian Grand Prix.