No way “okay” or “no” are found everywhere, nor “chocolate”. In the West, maybe. But even right here in Europe, we have the Greeks saying “ne” and meaning “yes” (whereas “no” translates to “ogie”).
And if my old Latin teacher hasn’t been misinforming me, the Romans of yore actually didn’t have words for yes and no at all. They’d use something like “I do” and “I don’t” instead.
The fact that a word has cognates in many related langauges doesn’t mean it’s universal, not even almost. It just means one word spread from one language to a number of others. That’s just a historical accident. Consider also that nobody on earth used those words before they spread around like that. (Somewhat less applicable for “no”, I guess.)
“Universal” means everyone, everywhere, always. There are certainly aspects of language that are universal in that sense – modern linguistics is all about identifying, relating and explaining those aspects – but words are usually language-specific.
Still, there’s indeed “mama” and “papa” that are pretty much universal, for the reason @morphail explained. Although even there, in Latin, “mamma” means not “mother” but “breast”. I think the ancient Romans assumed the child was asking for milk instead of addressing his mother.
And to repeat another thing that has already been said, there are also interjections like “ooh” and “ouch” and the like, but it’s debatable to what extent these are words and not just sounds. I would hesitate to consider them part of the language proper.
Looking at it in another way, I’m pretty sure there are things that every last language has a word for, things like “man” or “sun” or “day”.