You can forgive only when asked for forgiveness. When someone asks, you have a choice - to forgive or not.
But how do you forgive when the other person has not even asked for forgiveness? He has not even accepted he has done a wrong thing. How do you forgive that?
We often feel hurt when not being asked for forgiveness. Our ego hurts.
But the beauty to bury this hurt lies in forgiving the person when he did not even say "sorry". He did not say "sorry", but you have already forgiven in your mind. You feel light, without the burden of hurt.
Accept the apology you never got.