I'm with Tamrock on this one. The multiple inner edge-pattern matrix looks like coral, and not a breccia or conglomerate composed of fitted angular-sided stones.
Stingrays, mantas, sharks ... they can have the weirdest smiles sometimes.
When these break up into little platelets and are ground up and down a sandy beach they can produce some mysterious oddities.
If your item is a stone, then this is probably not it, but, if your find is weirdly man-made-like and you can't quite make out the material ... then we might also consider these as a possibility.
It has the look of being fossilized coral... Look up Petoskey stone, it’s consiered the Michigan state rock and has some similarities to your stone... neat looking either way!😬