According to what you said, that man should really like you, but now you have a sweetheart, and now it's between choosing and being chosen. This feeling is hard to give up.

If you reject that man intentionally or unintentionally, you may not be friends in the future, because once a man secretly loves a girl and can't get the woman he loves, he will ignore her in the future for fear of being hurt. I hope you can refuse him rationally and tactfully, and let him feel that you don't like him, but want to be friends with him. I hope he can understand your heart. Give it a try! The sooner the relationship is resolved, the better. If it drags on for a long time, it will be bad for both sides!