It depends on the nature of the story. If its satirical, etc., then thats considered fair game to use copyrighted material, if its just a little drop-in cameo for amusement's sake you might be able to get away with it as far as copyright goes due to certain justifications you might be able to use--but as far as writing an entire story around a Star Wars character, or having them prominently involved in it, in a straightforward dramatic fiction sense, then sorry you are out of luck because LFL doesn't licence out its material this way, unless you write it in co-operation with them and they don't really take unsolicited proposals from private authors who likely don't have agents or publishers.

You could just do what some people do--change the names, alter some of the details and make it into your own thing. The line between "heavily inspired from" and "ripoff of" is a fine one when it comes to this. I mean how many Boba Fett clones have we seen, but Boba Fett himself was really just The Man with No Name (In Space).