Before you get there, the bones would have been used as clubs and sharp broken bones used as proto-spears or knives.[1] Then after some period of time, it would seem reasonable that already recognizing the utility of the bones that a slightly more evolved creature would start to put the pieces together (pun intended) and find uses for bone chips/flakes for ever more effective tools. I can't even imagine how much time must have passed before this came together to get early us even that far.
[1] Which in turn would have come about after a long period of time just using rocks before those evolving primates discovered their advantages as tools/weapons.