So finally, I stumbled onto a new nice expression (as opposed to just a word) and this time...I didn't even know the English idiom!
So, here we go:
Reading: mekuso hanakuso wo warau
Meaning: translates to the English idiom "the pot calling the kettle black", or plainly "look who's talking!"
Literally: for the sleep in one's eyes to laugh at the snot in one's nose
Nothing more really to say about it...