Sure you can sell it. Every DMV is different but in general what seems to be required here is for you to give the new buyer your title + a Request for Duplicate Title all filled out by you. In this way, they submit both forms and get a title in their name, and you get skipped.
However, somebody has to pay the back registration unless you formally registered the vehicle on a "non-op" certificate. If you didn't, the buyer is going to get stuck with a year's or more registration fees, and if you don't tell them about this they are going to be very unhappy with you to say the least.
I'd go to DMV and just explain your situation and let them give you the right forms. You can either settle up on the fees or take something off the price of the car so that the new buyer can pay the fees.
No big deal here.