You bury the knot the same way as in regular hand quilting. If the knot won't pop through you may need to make the hole slightly bigger by using the tip of the needle in the hole where the knot should go. Put the needle in and sort of wiggle it around a bit. This will move the threads of the fabric aside and the knot will slip in. I would also make sure the knot is not too big. A quilters knot is ting compared to a knot created by rolling the thread between your fingers.