[jhv48]

That's a head scratcher. If it's in the pan, if there's any damage, it's already done. Almost looks like a broken piece of valve seat. Any weird or unusual noises lately?
If not, do a leak down or compression test and if all checks out ok, I personally, would try to forget about it and go for a drive. If it's serious, you'll know soon enough but I doubt it. Doesn't look like bearings, cam, piston, rings, lifters, etc.

Good luck sleeping.