That spot on his nose really does show a lot about the characters...
Ron's poor and dirty.
Mrs. Weasley's a typical mom (did your moms ever spit on a Kleenex and then attack your face with it when you were a kid?)
Hermione notices little problems, and it kind of establishes the dislike between them at the beginning of the series.
Harry notices and really doesn't care.
About Ron's nose, though... in the books, lots of long noses are mentioned... Dumbledore has a long nose, Ron has a long nose, Dobby has a long nose... Winky has a nose "like a tomato"... Snape has a hooked nose. Wonder if there is any connection between noses (also fingers? long fingers are everywhere)