I can't add much more to what has already been said except to reassure you that you are not alone. What happened to you and your Dom happens to a lot of first timers. Woodsman and I have been there. It is difficult to gauge how hard to hit and the effects the blows will produce. With practice he will learn. Both of you need to take this as a learning experience and go on. Don't let it stop you, just let it slow you down a little and proceed with care.