Those are very minor sore hocks. You can either put bunny balm, or neosporin(original) on the hock and that should help it heal. This is an article I found explaining how sore hocks are caused.
"Improper flooring - Rabbits need soft, preferably malleable flooring that will mimic the natural texture of the earth as much as possible. Wire flooring that doesn't have sufficient support underneath is not appropriate, as it can cause the foot to bow unnaturally. (Wire flooring with proper support is all right as long as you have a clean litterbox and soft bedding on top of it.) Wood, tile, or linoleum flooring can also be problematic, as it doesn't allow the foot to bend the way it does when it's pushing off against earth or grass. Cages with slick plastic bottoms are especially bad for a bunny's feet and joints. Lack of traction can cause painful problems in the pelvic and pectoral joints, leading to arthritis, and even "splayleg."
An indoor rabbit needs soft cotton mats with rubber backing to provide enough traction for healthy locomotion.
Obesity - A rabbit with too much weight on her body will often not be able to stand correctly, and may put unnatural pressure on points of her feet that are not meant to support much weight. This can cause sores.
Arthritis or other skeletal problems - Pain from arthritis in the pelvis or spine--or skeletal pain for any other reason--can cause a rabbit to posture in an unnatural way, resulting in pressure on delicate points of the feet.
Insufficient fur padding on the feet - Any cause of fur loss on the soles of the feet (e.g., mange, friction from improper flooring, contact allergies etc.) will deprive the rabbit of the natural padding she needs to protect her feet. Rabbits have little or no fat padding on the bottoms of their feet; they rely almost exclusively on a thick pad of wool to protect them from impact and friction. (NOTE: Some rabbit breeds, particularly Rex rabbits, have very fine fur that doesn't hold up well to friction. These breeds seem particularly prone to sore hock problems.)"
Also keep in mind in the "wild" rabbits nails would sink into the ground allowing the foot to rest evenly on the ground. If you have a solid floor this will make the rabbit walk on the back of the foot(hock area) which can lead to sore hocks. So you might want to put a natrual type of bedding in the cage. Or something like a towel, or resting pad (Pictured below) All of these things are inexpensive and will give your rabbit more traction than it has now. You can purchase a resting pad from bunnyrabbit.com for $3 or there is multiple other ways. The main thing right now is to get some traction into that cage.
Also wire cages do NOT always cause sore hocks in rabbits, if certain requirements are met. This is a good link to read- http://shinysatins.weebly.com/wire-floors.html
Remember a wire cage is just as bad as a solid wood, tile, or linoleum floor. All types flooring have certain requirements to make it safe for your buns feet.
I have wire cages (14 gauge wire), and plastic grid type cages(they are slippery, and allow the foot to rest evenly, they are like a wire cage except its plastic and the holes are less than .5" x .5") My grandmothers house rabbit however got sore hocks so it also depends on your rabbit as well. Hope I've helped