Dear Miss Healing:
Welcome back, good to read that you are in the process of healing, as your screen name suggests.
You asked how to kindly and respectfully end the very short dating relationship with the guy you met recently. My suggestion is that you let him know in-person, maybe over a beverage of some kind, that you enjoyed his company very much, but you have decided to resume a previous relationship instead of pursuing a new relationship with him. Tell him that you know from personal experience that rejection hurts, and that you are therefore very sorry to hurt his feelings. Tell him all this with a sincere and empathetic facial expression and tone of voice, and not in an over the top emotionality, best you can.
anita