If a person did not mean to hurt me by certain actions, does this mean there was no injustice and therefore there is nothing to forgive?
Sometimes even if a person did not intend to hurt you, the actions themselves can be insensitive and hurtful and therefore you can forgive. As an example, suppose someone was texting while driving and runs into your car. Although the person did not intend to cause an accident, that person still should have been paying more attention. The intention to do wrong was not there, but the necessity to be paying close attention also was not there. If the victim sees this as negligence, then the victim can go ahead with forgiving. Wrongful actions without bad intentions still can warrant forgiving the one who engaged in those actions.