the doctor told you that all newborns around this age and this result is normal.
so dont worry yourself, your going back to see if it has changed, and im sure the doctor will tell you what to do next.
he could just had a little cold or something.
if it were very very serious i do not think you would be going home and waiting for your next blood test to be done.
just keep the little one warm, maybe put a hot water bottle under a blanket and place it becide him, keep him hydrated[breast milk or formula] and wait for the blood test, and go to the doctors if you feel you have to.
good luck.