I know you are trying to avoid the vet, but- I think it would be better to go ahead and take your kitty in and get whatever it is taken care of, than wait, and a bad infection of some sort develop there. That would be more expensive to treat down the road
How long has the kitty's chin been like that? Does kitty scratch at it?
Plastic food dishes are a big factor in feline acne. Even if you scrub, soak etc... bacteria gets trapped in the scratches that accumulate over time on the bowls due to washing./wear and tear. My cat had acne once- I changed her bowls to all ceramic, and she has'nt had it since
Here are a couple good article on the subject:http://cats.about.com/cs/healthissues/a/acne.htmhttp://www.cat-world.com.au/FelineAcne.htm
This is a good page for every cat owner to have!!!!! It has some details of ringworm and other conditions that can mimic feline acne http://www.thepetcenter.com/exa/fd.html