What happens if the commercial vehicle that you were driving had no insurance and you were involved in an accident?

At the very least, an astronomical fine.

Pray that any other vehicles involved were covered with "uninsured motorist insurance". This is coverage that pays the injured parties an equivalent amount as the at-fault party's insurer would have paid had there been third-party insurance. If not, and assuming that you were the driver/owner of the at-fault vehicle, you would ordinarily be liable for those damages that were proximately caused by your negligence or that of the person using the vehicle with your permission.

If the injured party had to rely upon his/her uninsured motorist coveragem the paying insurer would have a right of subrogation. This means that it "inherits" the injured party's right of action against you for the purpose of trying to recover that which it paid. The same theory would apply to property damage payments that the insurer made.

Furthermore, depending upon the size, weight and consequent type of registration of the vehicle, the State or Federal Departments of Transportation may become involved. If it were a vehicle that came under its/their jurisdiction, there may be insurance requirements that had to be met that are different (greater) than those applicable to personal vehicles. Failure to abide by them may carry substantially greater penalties.

Depending upon the jurisdiction, a Financial Responsibility Law violation may be triggered. If so, this could result in the suspension of the tags of the vehicle and the driver's license of the driver until payment of damages is made.