It depends. An individual can put a lien on a car only if they receive court-approved judgment or if they are a mechanic.
A lien is a claim placed on property—in this case, your car—to ensure a debt is satisfied. If the debt is not paid off, you can repossess your car from the buyer. In general, banks, junkyards, and larger organizations place liens on vehicles. However, individuals like mechanics are able to put a lien on a car to ensure the work they perform is compensated.
The only other way an individual can file a judgment lien is by winning a court case against a debtor who has failed to pay them. This means you will have to sue your debtor in court. The court will then order your debtor to pay off the amount they owe as well as additional interest and court fees. This also grants you the legal right to repossess your vehicle if the debtor fails to pay.