Yes. Even if the taxicab accident appears minor, you still need to call 911 immediately. Many serious injuries, including brain or head trauma, do not show any immediate symptoms. This means the longer you wait to get help, the more dangerous this injury can become. However, when EMS arrives at the scene, they can quickly check you over and get you to the hospital if needed.
In addition, you want the police to come to the scene to create an official record of the taxicab accident and obtain all the necessary evidence such as driver information, license information, insurance information, and registration details. That way, if you could not get this information from the accident scene, you will have this information in the police report if you decide to pursue a legal claim.