Campbell was sent off for raising his arm last Saturday at Crystal Palace.
"It was stupid of me and I have apologised to the manager and the other lads," said Campbell.
"Of course I haven't helped my cause at all, I'm missing games that could have given me a chance to get back into the starting line-up.
"I can only say it was one of those things that happen in a split second when you're not thinking. I feel I've let people down.
"But the only thing I can do is go up to Sunderland before the ban starts and give everything if I get a chance.
"It would be fantastic to get a goal and help us get a victory up there."