I've seen in some movies the phrase 'look at you' being used.I've heard 'look at yourself' but never that.Is that makes any sense?What's the difference between the two?
Both are correct.
I'm native to a country where "look at you!" means more physical.
Look at you! Oh, God. Your nose is bleeding!
Look at you! What happened to your skin?
And, "look at yourself!" tends to be non-physical.
What?! Did you say that I'm a moron? Look at yourself!
(but I'm unsure if this applies to other countries.)
So, it depends on what you really want to express. Sorry for using a bad word.
To me, there is a difference. "Look at yourself!" is literally a command to look (though "look" might be metaphorical - it may mean something about "think about what you look like").
Whereas "Look at you!" cannot be a command, and I hear it as elliptic for something like "Will you look at you!" - an expression of surprise. I hear it as parallel to "Will you look at John!" - in a way, it is addressed to a different "you" (though there need not actually be anybody there to address).
"Look at yourself" is a direct, grammatically standard statement. You are ordering or encouraging the person to examine himself. It may be literal, for example if you are pointing out that the person is dirty or improperly dressed. "Your clothes are a mess! Look at yourself!" Or it may be figurative, you may mean that he should examine his own behavior or motives. "How dare you accuse me of being greedy. Look at yourself!"
"Look at you" is a more idiomatic expression. The speaker is saying that he sees something notable about the person he is addressing. For example, "Oh, look at you, all dressed up for your first date!" To the extent that you can make literal sense of it, the speaker is instructing himself to look at the subject.
That is, "Look at yourself" is a command to the person being addressed to examine himself. "Look at you" is an exclamation where the speaker notes that he has observed something about the subject.
You would never say "look at you" to instruct someone to examine himself. For example, "You need to clean yourself up! Look at you!" would be wrong, no fluent speaker would say that. Likewise, you would never use "look at yourself" to express your own amazement at someone's appearance.
There are cases where either would be appropriate. Namely, if it would make sense either to instruct the person to examine himself, or to express your own surprise at his appearance. But the meaning is different. "Look at you! You're a mess!" means "I am surprised that you are such a mess." "Look at yourself! You're a mess!" means "You should examine yourself and you will see that you are a mess" (probably with the implication that the person should clean themselves up).