Defining tool use is subtle. Here's one defintion:

"... the tool is a detached object (rock) used to procure some thing (food) ordinarily incapable of being accessed without a tool.". Also it is "manipulated independent of its location." [0]

Rubbing against a tree is not tool use. Similarly, dropping a nut on a rock is not tool use, but dropping a rock on a nut is.

It gets a bit more complex: You can pickup a stick and use it (similar to the cow); you can first prepare the stick by stripping leaves and branches off (some primates); you can bend the stick into a useful hook (New Caledonian crows).

Look up corvids and especially New Caledonian crows. they are pretty amazing; in some tasks they apparently outperform all primates except one particular species.