A person is sick, send a message to care about him. He replied, thank you for your concern. Let me not worry about what he said.

Just this short dialogue in this scene doesn't mean anything. It depends on your previous relationship and communication. Just looking at the landlord's question, the reply is too normal and quite polite. Not very close friends. If it is iron, I won't say thank you for your concern, but I will definitely say the second half. I am a man.