@JWB, I have one Easter Egger that has had repeat problems with bumble foot. I have wondered if the EE"s I have are not susceptible to it as they are the only ones affected. Alaskan has been lucky if he can put the treated chick back on dirt without further treatment. Not so here.
The key components to treatment are soaking the affected foot in warm water (Epson salts even better). I clean with my fingers feeling around the foot finding what is tender and what is not...and then I actually pick at the scab on the pad (it could be inbetween toes...I didn't see the scab on your pic. After a 15 minute soak, it should pic off fairly easily. (some people say not to do that, to cut around it to preserve getting the core out. It depends how long it has been infected, how much matter and puss is there to clear, and if the kernel will come out whole.
I think the very best treatment after the above is to spray VETRICIN into the whole, and put a gauze pad and then wrap the injured claws between toes with horse leg wrap....or human stretchy wrap bandage...the idea is to protect the hole on the sole of the foot with padding and make a barrier to dirt.
I have seen an excellent "operation" for bumble foot if you google there is a do it yourself video by a feather chick. I even saw a primitive clip from South America in which a man treated his roosters with soaks, a salve made of soap, and binding the foot with strips of old sheet padding the sole and tied around the leg. Care taken not to inhibit circulation. He left the bandage on for a month.
I have borrowed a disposable 4mm biopsy tool from my dermatologist. (It is a round razor sharp blade that makes a little clean "hole" the size of the tool when it is rotated back and forth. I've never had to use it. But it is how it is done by a vet.
The earlier you catch it and treat it the easier. If the kernel doesn't come out, it will probably come back. Chickens are amazingly cooperative when you soak them and work on their foot. Relieving the pressure makes the pain so much more bearable for them. Vetricin is NOT cheap, but it is the best tool in my first aid kit. Good for so many little things..wounds, skin problems of all kinds. Safe, nontoxic, kills germs, works on bumblefoot after soakings. You may soak a few days in a row, or if you get the kernel out the first day, and clean and bandage foot and just leave the bandage to get nasty. Watch the chicken put weight on the bandaged foot.