My dog has a growth on his upper arm and I'm not sure if I should be concerned... It looks pimple-like and it has been getting bigger over the course of the past few months. It is pinkish in color and round but smaller than my fingernail on my pinky finger. It does not appear to be painful even if I touch or squeeze it and he does not attempt to lick or bite it. Anyone have any ideas what it could be?