That's a bit naughty, Yur fitter couldn't be bothered altering the drain after removing the old bathroom suite. Without pulling it all apart the only thing you can do is remove the toilet pan again and try to get a multi-quick adapter to offset the drain enough for the systern to go back to the wall.
Failing that you could form a box or dummy wall section behind the systern forming a ledge/shelf a couple of inches above the top of the systern, and tile it to match the walls.