He can't help but worry about you. You were also a victim of the Joker along with him, you both got out of there, you both survived but he can't help but want to protect you from everything, especially because you decided to help him in his fight, but he is terrified that something happened to you.

“Tomorrow I will patrol alone.”

He said in a commanding tone, even though he was always distant, you knew he did it because he cared about you.