A core wound may begin in a past lifetime or if may be a past event in this lifetime. Either way, the past is the past and when a core wound is present, it means that the core center of your being is operating from a place of wounding, rather than love.
Before your Soul incarnated, it was asked to choose your parents and your major life experiences. These choices were based on karma from your previous lifetimes and the lessons you need to learn in this lifetime. The reason you learn lessons is to move you closer to Enlightenment each lifetime.