First thing you should do is just try any other ethernet cable, to rule out a bad cable. Ether cables are fairly delicate and shouldn't be bent too sharply. Are you seeing "No cable connected" in the Network control panel? If you still get this message with a different, known-good cable, then your Ether port might be toast, but first you should try zapping the PRAM, resetting the NVRAM, and booting to a different system, to rule out software.
If your port appears to have died (I've had this happen a few times) you can get a USB-Ethernet adapter like this one: http://eshop.macsales.com/item/Macally/A...
Of course, first check ifixit to see if they have something like it!
Zap PRAM: reboot while holding down command, option, P, R. Keep holding down till you hear 3 chimes.
Reset NVRAM: hold down command, option, the letter O, and F. You'll get a while screen with black text. Type "reset-nvram" and Return. Type "reset-all" at which point the computer will reboot automatically.