Personally, it doesnt look like fow pox very much to me, but, I could be wrong. . I would agree with Wyorp, and suggest leaving it unless it develops into something more noticeable. In which you can take the precautions above.
Could you post pictures of the lesions?
Generally, if only one or two are affected out of a whole flock you can vaccinate to help prevent further spreading within the flock, and reduce clinical symptoms. You can get the fowlpox vaccine here, and administer it via the wing/stick method ...