Do I need to contact my own insurance if the accident was not my fault?

Yes, you should contact your insurance agent if you were involved in an auto accident, even if the accident was not your fault. At that time, you should ask for a copy of your policy, including the declaration page (listing your coverages). You may have benefits such as medical payments coverage or wage loss coverage for which you have paid premiums.
Also, if the person who caused the accident turns out to be uninsured or under-insured, you may have applicable coverages under your own policy.