I've heard that the best antibiotic to give is injectable Pennicilin G, given intramuscularly in the side of the breast. There is info on this somewhere on the page linked from my sig.
As inflamed as that looks, you might also end up wanting to soak in warm water with Epsom salts, lance and drain pus if possible (It can sometimes be almost impossible to find a pus pocket even with multiple tries. But your hen's foot looks swollen tight enough in some spots that you might be able to locate one successfully.), and/or apply Neosporin to absorb through the skin and wrap with bandage (Be sure to change bandage every 2-3 days at least).
Ok, I went to southern states today and all they had was just penecillan so I got that! I need to know how to do it and where to do it also! Also, Is penecillan the same a penecillan G or is it sufficent??? Also is it for poultry? And do I give it to her by weight???Also how many times do I give it to her?
You just want to make sure it isn't the "long-acting" (48 hours) kind. If the label doesn't say to only give it every other day, it is probably a fine kind to use. The label will usually just mention cattle, but it is fine for chickens.
I would give it to her a minimum of 5 days in a row or up to a maximum of maybe 8 or 9 days. It might improve effectiveness if you can break the dose down and give 1/2 dose in 2 injections each day the first 2-3 days, but it isn't essential.
Dose per weight info is listed on linked webpage.
And I've found bumbles on the toes to be especially hard to get rid of. Good luck, the best thing to do is open it up with a razor blade and get that puss out. Getting the puss out gets rid of the infection and makes the foot heal quicker. I wish you strong stomach, my friend.