Bumblefoot often occurs after some other trauma. Birds may incur damage when jumping down from a perch, or they may get a cut, scrap or splinter of wood in the foot. The infection is often caused from Staphylococcus aureus bacteria which is nearly everywhere. However, it doesn't become a prpoblem until it can gain entry through a cut or injury.
The infection usually causes a solid core that looks like a cheese-like material. This core needs to be removed for the foot to heal. Cut the core out by opening the bottom of the foot enough to get the core out. once that is done, clean it by using hydrogen peroxide one time only.
After the core has been removed and the foot cleaned, keep the chicken in a clean environment for a few days. Put the bird in an area with clean shavings. Chickens usually heal very well, so it should get better quickly. Do not try to wrap the foot, because it won't work very well. You can continue to disinfect the foot with a disinfectant such as betadine, but don't continue using the hydrogen peroxide as it will damage new tissue.