My legs hurt in the morning?

I'm 13 years old and right now I have vacation. I go to sleep later than I usually do and I try to sleep more so that I can get my rest. However when it's around 8 or 9 my legs start to hurt. I fall asleep for a bit and I wake up with the small ache. My legs start to get restless and I start shaking them. Eventually I just can't fall asleep so I get up tired. The ache is somewhere behind my knees in that area. What should I do?