Yes to me it sound like the star nut need to be replace . If for any reason you can't do it yes take it to your LBS to do . Here how it done ,
Park Tool Co. » ParkTool Blog » Star Fangled Nut and Expansion Plug Installation . and here a video on youtube .
https://www.youtube.com/watch?v=K9Dy11NGBIEwhat you looking for start about 1:20 sec in on the video .