is the area wet and does it stay wet no matter how much you wipe it. that kinda looks like a hot spot but it is in an odd place. has anything changed since the move beside the house. food, or laundry detergent or water bowl. bullies can get stressed out with just a simple change but it could also be food related and since he is chewing on his back feet also it may suggest an allergy. does he smell the grass or anything else alot perhaps he is allergic to something outside. perhaps some povidone or some hibiclenz from the drug store to clean the area then put some desitin on it afterwards. id be looking at a vet visit if it doesnt clear up soon.