Yes, of course it is fine.
You should be aware of how both slang words and figures of speech become popular. Not too many syllables, short and punchy, simple and quickly recognizable with a clear meaning, even if broad: "Cool" as an expression of approval began in the 1940's Jazz culture, originally as a type of mellow relaxing music people liked, and gained prominence quite quickly and has stood the test of time, in use by multiple generations since then (80 years), most famously by the next generation coming of age in the 1950's and 60's.
Every generation makes up their own slang words and figures of speech. Anthropologists suggest this is part of the coming of age process; code the adults are intentionally unaware of; even if nothing has changed for this generation versus their parents. The biological urge, from puberty and for a decade, is to engage in romance, sex, and family building, which necessarily means escaping parental control and scrutiny.
And that in turn requires keeping secrets away from the parents and their agents (like teachers).
Of course new technology, like texting, are also an opportunity to invent new terms. LOL, Selfie, etc. Some of these take off, others are used briefly and fade out.
If you are doing this fictionally, keep in mind you don't want to use them so much the reader cannot understand what your characters are saying! That is not entertaining.
The first time you write a new slang word or figure in speech in use, try to make the meaning fairly obvious through context, or find some excuse for another character to define the term you are using.
Readers will cut you some slack on terms they don't understand, but if you keep them reading gibberish for pages, they will give up. They want to be entertained, and being confused and not understanding what people are saying is not entertaining; even if in the author's mind it is all clear.
Of course it is to you, the author, because you invented the words and meaning! If you don't find a way to share the meaning with the reader, don't expect them to work too hard to figure it out.
A critical part of being an author is being able to put aside what you know about the world and characters you invented, and read like a reader seeing it for the first time.