"asymptomatic" in the Covid context means "no external symptoms". One of the quirks of this disease is that it does damage to the lungs and reduces oxygenation

"asymptomatic" in the Covid context means "no external symptoms". One of the quirks of this disease is that it does damage to the lungs and reduces oxygenation without any obvious external signs (see the reports from doctors of people texting when their blood oxygen levels were otherwise extraordinarily low) and there are now reports of people having lung damage when they otherwise did not present as sick. So yes, it appears that it is possible to have long term damage even if it didn't seem that you were sick at first.