Is this sentence OK?
I mean it's so buzy.

It's buzzing in here like a hornet's nest.

Question

Is this sentence OK?
I mean it's so buzy.

It's buzzing in here like a hornet's nest.

Answer

I think you mean “it’s so busy.”  Usually we say “there’s a buzz in here”, but that sentence is okay.

Answer

The first sentence is incorrect, because buzy is not a word. However, it would still make sense with context.
The second sentence is OK.
Both sentences have similar meanings. Just remember that "buzz" can mean either the literal sound or conversation, so these sentences may have different meanings in different situations.