A single leaf spot is not a cause for concern. It looks like the roots are substantial enough to be moved into a small, pot filled with a porous, soilless potting mix. The pot size should be no larger than the glass container it is now in. It is better to have it tightly potted rather than providing extra room for the roots to grow.
Making the transition from water to the soil is tricky and not always successful. You have to maintain the right balance between water and air around the roots. That is why a small pot and a porous potting mix are essential. Do your best to keep the potting mix damp but not wet. Keep it warm and about 3 feet from a sunny east window.
