Smith sustained the knock in the moments prior to being floored by another short delivery by Jofra Archer - a blow to the head which required him to retire hurt and undergo concussion assessments
Steve Smith has been cleared of any fracture after being sent to hospital for an X-ray on his left arm after he was struck by a Jofra Archer bouncer at Lord's.
Smith sustained the knock in the moments prior to being floored by another short delivery by the England paceman - a blow to the head which required him to retire hurt and undergo concussion assessments.
He passed those tests and returned to bat, eventually being dismissed by Chris Woakes for 92, but he was still experiencing pain from the earlier incident.
Smith had received ice to the problem area to deal with substantial swelling and bruising, and did not appear on the field when England began their second innings after tea on day four.
Cricket Australia confirmed the former captain has been sent for an X-ray, and later said that no break had been found.
Smith is icing the injury, with the intention of being able to bat if required on Sunday.
England finished day four on 96 for 4 in their second innings to lead by 104.