A goalless draw in Basle was enough to send the Swiss to Russia after a controversial 1-0 first-leg win in Belfast.
Seferovic missed a number of gilt-edged chances to make the game safe and Ricardo Rodriguez had to clear a stoppage-time Jonny Evans header off the line to keep qualification safe.
By that point, Seferovic had been substituted to a chorus of jeers and whistles at St Jakob-Park and the Swiss coach was frustrated by their actions.
"It was a pity," Petkovic said. "We should learn some things from the Northern Irish fans.
"But now I do not want to incite arguments, but to enjoy the moment that we are definitely in Russia."
Switzerland won their opening nine group games in qualifying, only for a defeat to Portugal in their final fixture to send them to the play-off.
And Petkovic was delighted with the determination shown by his side to put that disappointment behind them.
He said: "I am very happy with my boys. With everything they have done, not only in the game against Northern Ireland.
"My team has an excellent spirit, positivity and will. They always want to achieve the highest goals.
"I hope they will be even hungrier in the future. It will be a highlight for us to be present at the World Cup."