Where did he get that cut? He didn't have it a few days ago. Aloof as he may seem, Minho is actually one of the most observant shanks from Group A. So when he woke up one day after the Gladers got out of the Maze and noticed Newt's cut, he got curious. The only time Newt could have gotten that cut is between the helicopter ride and their arrival at the facility. They were practically together 24/7 so he would have noticed if Newt got hurt.
One day, Minho found Newt alone in the dorm room after having just showered. When Newt looked up for a brief second, his cut caught the other boy's eyes again. Minho was itching to find out, so he asked.
"Hey shank, where did you get that?"
"Get what?" asked Newt as he put on his top.
"I could've sworn you didn't have that cut on your face when we got here. So tell me, where'd you get it?"
Newt stood and touched his cheek. He seemed to have forgotten that the cut was there in the first place.
"I don't know, probably nothing."
So Minho dropped the subject… for now.