@pleonasm - No, if they are looking for one pupil larger than the other, it means they are looking for something more serious than concussion (although concussion can be both more and less serious than people expect).
Concussion (they usually call it Mild Traumatic Brain Injury now) just means the brain has been shaken up. It has a wide range of symptoms, which can include everything from a mild seizure, to brain fog. Sometimes it's fairly serious and persistent, sometimes it's mild and goes away quickly.
But, if something is affecting the pupils, particularly if it occurs some time after the accident, that means there is a more severe problem going on and the person needs to go to hospital ASAP.