I would scrub till it bleeds and put neosporin on it heavily...then wrap them in vet wrap and change it often until its healed....need to see a better pic.
You need to be sure that it doesnt become bumble foot. There is staph infection everywhere and any open cut on the foot can get staph in it and form a bumble....
dont be afraid to scrub it ...dont be afraid if it bleeding....get the dirt out, coat it with neosporin ointment and then wrap it with vet wrap. Look in the bumblefoot stickies to see how to wrap. I use one long piece rather than cutting strips. Its a little uncomfortable for them to walk around in it, but it protects the feet.