I had the same thing happen to my 2008 Versa recently, the muffler flange weld broke. I took it to a local muffler shop and they cut out the whole flange deal and welded in a curved pipe for $50. It didn't appear that there was anything else wrong with the muffler itself, so yours may not need replaced either. However, if you can get yours unbolted you may be able to just weld the flange back on. I didn't really have a way to get under there to work on mine, so I figured $50 was cheap enough to not have to deal with it myself.
