Yes, that is bumblefoot. You will need to soak the foot in epsom salts to soften the scab for removal. Alternately you can apply decolorized iodine (any pharmacy should have) and wrap it overnight, that should also soften it. Remove the scab, and clean out underneath. Remove any core or chunks of pus. Since there is swelling on the top it may take some squeezing and manipulation to get all the pus out. The pus will be solid, and creamy white, not runny. Flush it out well with chlorhexidine (hibiclens) or diluted betadine. If any pus remains inside, it will regnerate. If you can't get the stuff out between the toes, where the swelling is, you many need to lance it from the top, but hopefully it will squeeze out the bottom. Fill the hole after flushing it out well with plain triple antibiotic ointment, cover with gauze or a telfa pad and wrap with co wrap/vet wrap to keep it clean and dry. I change bandages and reapply ointment daily until I know it's healing, then go to every other or every third day, as seems appropriate. I keep it wrapped until it's all healed up. Make sure the wrap isn't too tight, just tight enough to keep it on. I buy the 4" wide rolls of co wrap in the horse section at tractor supply and cut them down to the width and length I need. About 1" wide seems to work well for most chicken feet. If you wrap the foot, between the toes, and then a wrap or two around the ankle, it usually stays on. If you only wrap the foot, they will sometimes pull it off. After a while they get used to it and leave it alone.
Here's a link with basically what I do:
http://www.tillysnest.com/2015/12/non-surgical-bumblefoot-treatment.html/?spref=pi
