... literally. Nothing to worry about, though - this is an empty Blackbird eggshell.
The raggedy edge shows that it was chipped open by a chick, using its egg-tooth. Not a real tooth, but a horny tip to the chick's bill which develops specially for that purpose, and then withers away after hatching.
What's it doing on the lawn? The female Blackbird will have dumped it there after the chick hatched. A load of brightly-coloured eggshells lying around the nest would get in the way and also draw attention to the nest. Occasionally, the shells are eaten by the female, as they represent a lot of calcium which might come in handy for the next brood.