what have you been told by your GP? They must have had a reason to run a blood test
I can tell you that my son had blood tests following a non-blanching rash that also came up with low white blood cells. he then had a blood test every 3 months for 9 months before the results were normal again.
because nothing else was amiss the peadiatrician did not seem too concerned though of course it was a worrying experience.
The paediatrician or your GP (whoever arranged test) will be the people to advise you.
my daughter is 13, and she fainted at the weekend, she wasnt well at the time, but I took her to the docs and she was sent for a blood test, come back the same as yours, low white cell count, but this is due to an infection or virus, I spoke to my friend about it who is a nurse and she said not to worry, her sons has been like that a lot and theres nothing wrong with him!!! Hope this helps