Google has released the SMS bug fix[GRH78C] for Nexus S. The manual download is available here or you can wait for the OTA update, which will come on your phone pretty soon.

Instructions to manually update:

• Copy the file to your phone’s internal storage (/sdcard).
• Power off your phone.
• Hold down the VOLUME UP button and power it back on.
• Use the volume keys to navigate to recovery and press POWER to select it.
• When you see the “/!\” symbol, hold the POWER button and then press the VOLUME UP button.
• You should be presented with a menu and one of the options should be “apply update from /sdcard”
• Find the update file on your sdcard and then press the POWER button to flash it.
• Wait for the update to complete and then select “reboot system now”