Just a thought. But if you're wishing this never happened, it's probably better to stop it now than give it a few more chances. If he continues to fall for her while she feels nothing romantically for him, that's just leading him on. And that's a sure way to ruin a friendship. Just be honest with him. Most people would rather a little honest pain now than a to get invested in something and have a world of pain plus dishonesty dumped on them later.
I'd rather be hated for who I am than loved for who I am not.