Hello, and thanks for writing in.
It sounds like a localized area of infection, which could have come about for various reasons (i.e. puncture, spider bite, other wound, infected cyst or growth). Treatment for this type of thing usually involves cleaning the area well, oral antibiotics from your veterinarian, and possibly topical antibiotic ointment (i.e. Neosporin or triple antibiotic ointment). If the area is a cyst or growth that is infected, surgery may be required to remove the cyst or growth, in order to completely get rid of the source of infection.
I hope this helps.
Thanks for your reply. Anytime there is pus draining from a wound, I would recommend a visit to a veterinarian for appropriate treatment, so that the problem can be healed as quickly as possible. Having said that, if you were to clean the area and use Neosporin for a couple days, it would not likely cause harm. Then, if there is no improvement, visit your veterinarian for definitive treatment if needed.