If in fact it is not a worked piece of stone it would still be consistent with the type of natural stone tools used before some individual discovered what happened when a certain rock was struck and the resulting pieces produced a sharp edge. I think most scientists agree that natural stone tools, usually found near, and shaped by, water preceded worked stone tools. If you have a good museum or large college nearby you may be able to submit your find for evaluation as an actual tool. Otherwise you have found a rock you would not want to be struck with. Either way, good eye.