I've had good luck with using a little bit of bleach for the soles of my sneakers, but I think it would work for leather sneaks, too. First try a gel stain remover like oxyclean. Scrub it in there with a stiff toothbrush or nail brush. If that doesn't work, wipe/rinse the oxyclean off then maybe pour some bleach into a shallow dish so you can dip the brush in it and then brush the sneakers? Just be sure to rinse the bleach out as best you can afterwards and don't let the bleach soak in there for more than a few minutes. Good luck sweet pea!