I was in a car accident two days ago, the air bags deployed. i'm feeling extreme pain in my lower neck and back should i go into the er to be seen?

Yes: Yes.....you should be seen by your doctor/any ER doctor to rule out any trauma to any abdominal organ...close to diaphragm in particular....may be just because of seat belt

IMHO, Yes: Actually, I wish you'd have asked two days ago. Yes, be seen and keep a record of the findings. Injuries from such events can take some time to express themself and you should be examined and treated ASAP. I hope you feel relief soon!