Iodine is extremely painful on an open wound, though it is a disinfectant. It would be best to use the purple spray which is sold for the purpose in pet stores or agricultural stores, which disinfects, and colours the wound so it's not so obvious to the other hens. It's easier to apply without getting it all over the places you don't want it to go (including yourself, when holding a struggling hen!) if you spray some on to a saucer and then apply it with a cotton bud to a cleaned wound. You can also buy antibiotic powder suitable for animals or birds, which can be puffed on to an open wound (but be very careful not to inhale it.) Do you know what caused the damage in the first place? This is important as you may be able to prevent further occurrences if you could remove a possible source of danger. Also it might have started through extreme irritation if she has bad scaly mite on her legs (raised scales and rough leg surface, due to parasite burrowing under the scales.)
If she is pecking it herself, it sounds as if it's irritating her, possibly through infection or dust etc in the wound. When they scratch the ground, of course their legs get filthy and it's extremely difficult to keep leg wounds clean. I would bathe it thoroughly in warm water to which a little salt has been added (again, not too much as the salt will be painful if the wound is open) before treating it with spray. Then possibly you could bandage it to keep it clean. There is a kind of blue bandage used by vets which sticks to itself but can be easily removed from animal skin, hair etc, but I don't know what it's called.
Also you will need to invent a temporary pen for her to prevent the others damaging it and pecking her, at least during the day, you could return her to the coop overnight. If you have a big enough run maybe you could fence off a corner of it with some spare wire mesh, so she can see the others and not get isolated from the flock. I do this when one of mine goes broody. We chicken keepers do need to have 'hospital facilities' available, or at least thought out in advance, as this sort of situation inevitably occurs at one time or another.
