How big is it? Are there any markings on it? Where was it found, just a general location such as part of a state or another country. Also, a better focused picture would help.
It’s a homemade fishing weight/sinker. Chunk of lead with a hole punched through it for the line. Could have also been used to weigh down a fishing net or depth measure as crashbandicoot mentioned. I’ve found several similar ones while detecting old fishing holes.
Just seeing a pixilated image at this end. If you have it in your hand and can't tell what it is them we on the viewing monitors have a LOT less chance of determining what it is.