Need a diffrential diagnosis

u r right, it`s skin abscess . but i was asking about its origin . which is originated from infected sebaceous cyst , which was infected ."folliculitis " then it took this shape .it`s sebaceous cyst because it appears from the photo that it`s superficial lesion and it is pointing through a hair follicle.
for the treatment yes it`s treated by either local or systemic antibiotics . but this case is advanced one"abscess" it need drainage and irrigation.

Dear "UP.the wind" thank u for participating in our forum . and it has been great pleasure to see u contributing in one of my certain subjects.