When a vehicle is hit by a semi truck, the impact will often cause the airbags to deploy which can cause blunt abdominal trauma.
Even if the airbags do not deploy, seat belts are designed to hold the driver in place when they would otherwise be thrown from the vehicle.
The seat belt alone can cause severe chest pain, liver, bladder, spleen, or kidney injuries.
If an internal injury is suffered it is not always obvious immediately following the accident.
Never turn down medical attention, you could run the risk of becoming even more injured than you already are.