Take it to the dealer tell them what you found (show them the bits) and get the oil changed. .
Insist they save the oil and show it to you.
It may be trivial.
(I say that because if the engine is running fine.. it may be something like a oil splash tray or some other non-important thing in the engine. Or a bit of flashing from the engine block casting got left down there..
Anyway, if it is running no problem i would not be too worried.
It may be some bit someone forgot in there, and it got busted up by the crankshaft spinning.
If it was a bearing you would already be sitting with a dead frozen engine..
There is nothing down in the crankcase that matters much from being banged by a small chunk of light metal bouncing around. really. (well maybe the oil pickup tube.. but i bet that is fine since your engine oil light has not gone on..)
So as i wrote. do not worry too much. Just take the car to the dealer..
The oil dipstick goes straight down to the crackcase..
The only thing i can think of that it might be (if it IS an engine part) is some sort of camshaft chain guide or damper. That could break, fall down into the bottom, and the crankshaft could break up...