Some rabbits are more prone to foot abscesses for various reasons. It may be a conformation issue that leads to the weight not being properly distributed on the foot which can lead to tissue break down, old age, large breeds are sometimes more prone, thin fur on footpad, flooring that doesn't properly distribute weight, underlying health problem, rusty wire flooring, dampness leading to fungal or bacterial infection, or other causes.
Oftentimes, placing plastic mats in the cage help to relieve sore hocks. Belgian Hares are very prone to sore hocks, so I put feed bags in our Hare's cage when she began to develop sore hocks (She already had wood boards in her cage). I also used Desitin ointment on the sore. I change the paper feed bags frequently, and her feet have completely cleared up.
In severe cases of sore hocks, infection can spread up the leg resulting in fatal septicemia.
Do keep in mind that I "suspect" your rabbit developed sore hocks. Without actually examining it, I don't know if it is sore hocks or injury related.
Pam