Is it possible to have withdrawal symptoms from Oxycodone after only 1 week?

I had nasal surgery a week ago and was prescribed Oxycodone for pain. I only took it for about 6 days but now I'm having this horrible insomnia. Could it be withdrawal from the Oxycodone even though I didn't take it that long?

: http://alcoholdrugstreatment.info/is-it-possible-to-have-withdrawal-symptoms-from-oxycodone-after-only-1-week