to flank can cause trauma to the kidney as well as to the ureter
. You may need to stay in a hospital for close observation because of the risk of internal blood loss from an injured kidney.
According your history your son does not have features of renal failure
and he has mild hematuria
which is normal for most cases.
For minor kidney injuries, careful control of fluid intake and bed rest
are often the only treatment needed, because these measures allow the kidney to heal itself.
He does not need analgesics as he is not in pain.
But he may need Bed rest for 1 - 2 weeks or until bleeding is reduced.
He does not have any features of infection.
My personal feeling is he can keep in the home at the moment and observe for urine out put.
If things are getting worst you can take him back to the hospital.
Hope you got the answer.