Can someone identify this?

no you shouldnt worry.

That looks like it could be an old piece of buried infrastructure, possibly part of a water or gas line. The flange at the top and the general shape make me think it might have been a valve or a pipe connection point. It’s not uncommon to find these when digging around older properties. They often get left behind when systems are upgraded or rerouted.

If you’re planning to do more digging or construction in the area, though, it might be worth checking with your local council or utility company just to make sure it’s completely decommissioned and safe to handle. Sometimes old fittings like this can still be connected to something underground.