Proper tool to clean up cut corners in tile?

When I’m cutting tile into a shape that includes a right angle (an ”L” shape, for example, or a piece around a nitch etc), there is always a bit of the stone leftover in the joint after the wet saw. Usually I take a grinder to it, but because the cutting wheel is round and the angles in question are right angles, I can only get close to perfect 90 degrees angles. Is there a specific tool for this? Or is it just getting better with the grinder?