Here's a bit of info on feather cysts. http://www.poultrydvm.com/condition/feather-follicle-cysts.
I've dealt with ingrown feathers, and was able to make a small incision across the lesion to release the feather follicle. Then I squeezed out any fluid and painted Blu-kote on it. You can also...
Those lumps remind me of insect galls.
I have never seen such a thing on chicken feet. They don't appear to be bumblefoot lesions. While not your ordinary presentation of scaly leg mites, they could be that or something similar.
If they are a result of insect eggs, they could respond to oil...