It looks like a hard kernel that should dissolve with a liquid wart remover from the images I've seen but once you can get under it sure I'd go for topical antibiotics. Interesting that you say the etiology is an injury that becomes infected. Hopefully I'll get to see it and practice. Heck I'd even bet CLR would dissolve the colonies protective coat allowing you to get to the active infection to treat it and exposure to oxygen alone may be all it takes to do the bacteria in.
Hope one day I get my chance to practice.