I’d not open the door. You don’t know him so it’s not safe. I think you could either avoid him entirely or talk to him but not letting him inside.
We have a neighbor who for the longest time tried to get inside out place and followed us around. It was because I listened to her woes once. I had to stop acknowledging her at all for her to leave me alone. She still periodically bugs my husband, she is convinced he is a doctor even though he explained to her that he is RN, she said in her mind is the same thing. Lol She still stops him and says “doctor could i ask you for medical advice”. We try to avoid her
I usually avoid neighbors. I had some very bad experiences with neighbors. And I never let anyone inside unless I invited people ahead of time like family or close friends