Reasons why Neji wears gauze on his arm:
1.) It keeps his "YOUTH!" tattoo hidden
2.) He accidently used Byakugan on his arm and saw a blood cell that resembled Guy. He never wanted to see it again.
3.) He told Lee that he was stupid, and in return Lee stabbed Neji with a kunai. The gauze covers the scars.
4.) That arm is a fake. The other one was destroyed when Naruto spilled steaming hot ramen on it.
5.) Neji had to have an operation on his arm to remove three giant splinters as the result of Lee goofing off.
6.) Tenten told him to put the gauze on, and he obeys her every command.
7.) He was jealous of Sasuke.
8.) He was actually jealous of Lee.
9.) Guy told Neji that if he DIDN'T put it on, then he would sing. It's been on since that day in fear.
10.) He hurt his arm playing Wii.
"What are you two doing in my room?" Neji asked as he walked into his bedroom. Lee and Tenten were bent over a small book. Tenten whipped her head around.
"Ah! H-hey Neji! We weren't reading your diary!!" Neji's eyes bulged even worse that when he performed Byakugan.
"You were WHAT?!" he demanded. Meanwhile, Lee fell to the floor laughing.
"I cannot believe you would do so many insane things, Neji! Ha ha ha ha!!" Neji stomped on Lee's face.
"Shut up! Like yours were any better!"
Tenten did manage to keep down her giggles. "Well (heh) Neji, at least we (snicker) know why you two wear gauze."
Neji sighed and glanced down. When he did, he spotted a tiny bit of gauze on Tenten's leg where her weapon's roster was.
"Hey Tenten…what's that for?"
Tenten looked down, and smacked her face. "Aw man, not AGAIN!!"