Its rare that you can install hardwood under an existing toilet and just get by with a wax ring. Usually the hardwood extends past the flange to where you need to install an extender to bring it even with the floor and then use a wax ring. You may have a very small leak because the wax ring is not compressed enough to do its job correctly. The extenders can be bought at L. and HD and are a simple project.

I'll get my plumber in then and mention the extender...probably should not have let the floor guy install the toilet to begin with I guess....each trade has their own expertise.