Agree that you should not cover that. It is there for a reason, and if you ever need access to it you will cause a lot of damage to your floor. I can think of a couple of alternatives. Perhaps someone smarter than me can tell you better. See if a plumber could cut the pipe so that it is below the floor. Have said plumber create a lip of some kind, cut a round piece of 1/2" plywood and a corresponding piece of floor. Glue the floor to the plywood then put the "plug" over the hole. That way you can access the pipe if you ever need it and it won't be a trip hazard.