I think it’s the rim of the finger hole, which scatters light.
You could rotate the ball a bit …
In the past, I had many such experiences as you have.
The outcome of a render looks unnatural and every time you look you see (for you) these strange artefacts. Some are obvious, but others like this one are just as it is so.
This is how our brain works.
Look around you, in the real world, everything looks natural …
But look closer and try to explain the phenomenon in the way of Blender you see strange unexplained but completely natural light scattering and strange reflection effects.
Have fun, don’t think too much about this. Realism is very very hard to do.