Super-precise measuring, done with a Digital Caliper, is needed for determining with certainty whether a lead ball is a firearms projectile or something else. Depending on its diameter, in hundredths-of-an-inch, from smallest to largest a lead ball could be a buckshot, a pistol-ball, a musket ball, an artillery Canister-ammo ball, a Grapeshot ball, or a not-a-projectile (such as a fishing-weight or net-weight).
Until you can get that lead ball precisely measured and report the measurement back to us here, I'll make an educated guess based on what can be seen in your photos. You say you found it in a creek, which is a logical location for finding a fishing-weight ball. But, the only well-focused photo doesn't seem to show a slit cut in the ball... a slit would mean it's a fishing-weight. The ball appears to be perfectly-round, which suggests it could be a projectile. The ball's size in comparison to your fingers suggests that, if it is a projectile, it is a pistol-ball, not a musket-ball.
Also "meanwhile"... here's a chart of buckshot-ball diameters.