You fell down on the stairs and hurt your knee. Your girlfriend is worried, so you're reassuring her.
I just skinned it a little.
injury, simple past 
You're about to watch a basketball game on TV. There's a show before the game where the sports announcers discuss the game. They're talking about one of the players who suffered a knee injury last year. One of them says:
The question is whether his leg is fully recovered.
You're about to watch a basketball game on TV. It's the first game this year for the teams that are playing. There's a show before the game where the sports announcers discuss the game. They're talking about one of the players who got hurt last year. One of the announcers says:
Meyerson suffered a major knee injury last year that took him out of the game for most of the season.
Your brother cut his finger while cutting an onion. The cut looks serious, but he says that it's "just a scratch". You know that it hurts, and you want him to treat the cut correctly. You say:
Don't try to act tough.
injury, personality, set phrase, tough Your brother cut his finger while cutting some onions. There's a lot of blood coming out of the cut, and you're worried about it. You say:
That looks serious.
injury, stative verb, worry Your brother cut his finger. He just put a band-aid on it, but you think he should also use an ointment so that the cut doesn't get infected. You say:
You should put some stuff on it to keep it from getting infected, don't you think?
gerund, injury, medicine, stuff, tag question You cut your finger. Your sister wants you to put some medicine on it to make sure that it doesn't get infected, but you don't think that's necessary because you only cut yourself a little bit. You say:
No, it's just a scratch.
injury, just, set phrase 