Jimin saw the way in which your face had changed as you said good night to him but played no attention to it. He didn't process it properly because of how exhausted he was. He never did when he was tired a d found it hard to focus on things but did so to the point he would pass out. Tonight didn't seem to be one of those nights where he could do that.
About five minutes after you had left to go to bed his eyes opened wide in the realisation of what he had done. How had he not noticed the way your shoulders stood to attention at his voice and the way you started to shake profusely? He never ment to upset you. He was just tired of everyone going on at him all night.
He decided to go upstairs and apologise for his actions and try to explain himself. He crept up the stairs as quietly as possible as he knew that when you were in a state like this it could trigger another attack. He shuffled along the corridor to the bedroom and slowly creaked the door open.