Thank you for your query.
Following a fall from the stairs one can sustain head injury
. If the hospital staff did not find any signs warranting intervention they sent you home. However, the following symptoms and/or signs need medical intervention:
4. Abnormal movements including blurred vision
As the second visit did not reveal any abnormality I suggest that you can wait for a few hours more as your son "seems fine". In case any of the above symptoms occur then do take him to the hospital again.
I hope I have answered your query to your satisfaction.
Wishing your son all the best.