I’m sorry to hear this. Hopefully your insurance policy has what’s called “gap coverage,” which covers the “gap” between your property damage claim for your totaled car and the amount remaining on your car loan. If not, there’s nothing that you can do. However, you may be able to make up the difference through your personal injury claim.
Here’s an example to explain: You buy a car for $20,000. A year later your car is totaled in an accident. Its fair market value is determined to be $15,000, so the insurance company writes you a $15,000 check for the property damage. After using that $15,000 to pay off your car loan, you still owe $2,000 on your car loan. If you have “gap coverage,” you can use it to pay that $2,000.