search bumblefoot...does it have a little or big black or callus like spot anywhere on the toe? Google bumblefoot and look at the images.....it looks like mine did at first. if it is then its a staph infection and it needs to be soaked and opened....you can search it here and see what people have done or take it to a vet. But if you wait, and it is bumblefoot, it will only get worse and eventually kill the chicken. see of there is a callus somewhere that would be the initial scratch where it started.
Hope its not...my hen is healing OK, but its a real pain in the ass...
Be sure that you wear gloves and keep everything clean if you open it. It will have a hard plug and some soft and possibly hard pus under it that has to come out and then be packed with antibiotic...probably soaked...and possibly will need some systemic penicillin.
The group here can help...and meds are easy to get online...but if you have a reasonable vet, and can afford it, then by all means;-)