Without better pictures, and even a side profile it is almost impossible determine if this was a utilize tool. Take some close-ups, and provide better pictures of any sort of flaking that may exist.
Those flake removals are very common in many different types of stones. However, those flakes are not indicative of utilization. You will find this when rocks hit against other rocks, and people often attribute those to be worked. However those type of flakes just don't appear to be enough proof that it was utilized as a tool.
Perhaps you are right, perhaps you are wrong arrow492. But that sure looks like a classic thumbscraper to me. Some nice material too!
I bet there is only flaking on the one area shown and not all around though, evidence to the contrary of random rock chipping. Maybe we will see more and better pics, all I have seen this on is my phone, but I still see it.