It is a shame there is nothing interesting in the middle.
The pale area: it is common for flints to have different-coloured parts.
The slight banding in bottom photo (if it is really there): banding occurs in flints, though its origin is still debated.
The spherical shape: I don't think this is due to it having its origin as a spherical sponge (fossil). It may be coincidental, but it could also be artificial. Man used stones as ammunition (as has been discussed elsewhere on NaturePlus), but that's not my field.
It's really dissapointing that ther's nothing in there, but I learned from your answer so there is a good side to it too...
I had a surprise about the idea of creating that kind of ammunition from flint- that is broken into sharp pieces when you hit it (so it's not the first stone I would choose for creating spherical shape),