What should I do when the at fault party has no car insurance?

I got into a minor car accident, it was the other party's fault but he doesn't have car insurance. Because it was a rental car, my own car insurance is not going to cover. Now the rental car company is going to charge me for $3,000 for the damage which I did not have a chance to get a second opinion. Besides I did not use my credit card to pay for the rental since my credit line is not enough to pay the balance, I used my debit card instead. what should I do?