My son was stopped at a red light and a lady rear ended him. She gave her name and the Insurance policy # but had borrowed the car and is not covered

Since you do not mention that your son was injured, you can probably handle this matter on your own without the need to hire an attorney.  I suggest that you contact your own personal auto insurance company to make a claim under your uninsured motorist coverage to determine whether the at fault driver was truly not covered under the auto insurance policy of the owner of the vehicle.  Good luck with this matter.