Are his hocks severe? Are they broken? Sometimes in cases where the wound is broken vets offer pain meds. If they are just a bit red and sore looking you could try rubbing the normal blue vasaline (although your bun may lick that off as well). My rex has sore hocks, although they haven't gone completely I changed the flooring and bought puzzle mats, memory foam mats and other soft flooring to cover my tiles so it isn't as painful on his feet.
In that case try to make the main flooring soft, you could use memory foam mats, or those interlocking gym mats and cover them with bed sheets. Wood can sometimes make it worse so try to avoid hard flooring. Hope everything goes well. <3