You never told or even mentioned the topic to Miguel, but since you started dating him, he noticed some behaviors you had and couldn't help but feel upset, thinking that someone in your past had hurt you and that's why you acted in a certain way

"I swear I'll put an end to whoever hurt you"

Miguel said. Even though you didn't tell him, he could feel that you were still silently suffering from your past

"I promise I won't let that person who dared to hurt you get away with it"