Is Difference In Pupil Size A Cause For Concern In Children?

My 11 year old son was just hit in the eye with a football. The school nurse noticed that his pupils are different sizes. She checked on him again about 30 minutes after the injury. The swelling around the eye has improved and the pupil difference has improved slightly. She recommended contacting our eye doctor but the office is closed today. Should I seek emergency care because of the pupil size difference?