Is it the flex section on the exhaust?
looks like about a 6-8" long piece of braided steel tubing?
If so, then yes you can still drive it, it'll just be loud and annoying.
the part itself can be replaced, but it's better to just buy a whole new Y pipe.
check out these guys.. good parts, good prices.
http://www.warpspeedperformance.com/nissan.htm