Rejecting others is also a learning. It is your original intention not to hurt him, which shows that you are a kind girl.
First of all, I think you can keep a distance from him, give him such a sense of distance, and then gradually remind him, you can give him a small gift, or put a letter in it.
Such a gift does not have to be very expensive. You can go online and choose a small gift for him.
You can give her a crystal music box, which represents memory, and put your letter in it. It should make him understand your intentions, and he will retreat and stop pestering you. I hope it will be helpful to you. You can go and have a look at other gifts. I hope you will like them.