Sorry to here. I would leave some kind of night light on for him/her, at night at corse. These guys are skiddish if they are uncomfortable especially when they can't see. If its not eating it's probably cuz it's still stressed from banging it head on the glass. Just add some stress coat and let him be for a couple a days. Pretty sure it'll come around. Just make sure to put a night light b4 you go to bed. By the way how big is the tank?
Your tank is to small for your aro bro. If it's 12" i recommend you getting it a bigger tank now, the sooner the better. 3f long and how wide, regardless it is way to small. In a few months it'll be 14"-16" big.
If it's not eating, just stop the feeding they can go wks if not months without food. Tbh I can't stress anough about getting it a bigger tank. I think that's the main reason why its not comfortable imo.