1. Apologizing:

I’m sorry that/for…

I apologize for / Apologies for…

Oops, sorry / My bad

I should have / I shouldn’t have…

Responding:

That’s OK / It’s all right

No problem / No worries / Don’t worry about it.

It happens.

I forgive you / You’re forgiven.

I appreciate your apology. / I accept your apology.

Thank you for your apology.

Apology accepted.