Excuse meEver so sorry.How stupid/careless/thoughtless of me.
I apologize.I had that wrong.I hope you can forgive me.
I owe you an apology.I sincerely apologize.I take full responsibility.
I want to apologize.I wanted to tell you I’m sorry.I was wrong about that.
I’d like to apologize.I’d like to apologize for how I reacted yesterday.I’m (so/very/terribly) sorry.
My apologies.My fault, bro (US)My mistake.
Oh my goodness! I’m so sorry. I should have watched where I was going.Oh, my bad.  Pardon (me)
Please accept our (sincerest) apologies.Please don’t be mad at me.Please excuse my (ignorance)
Sorry about that.Sorry, my apologies. I had that wrong.Sorry. It was all my fault.
That was wrong of me.That’s my fault.Whoops! Sorry!
I beg your pardonMy bad (US)Excuse me for interrupting.
I was wrong. Can you forgive me?Pardon me for being so rude.