Knee and upper leg pain

[Deleted User]

I was wondering if anyone out there has has any advice on upper leg pain? At the moment I have an ache which runs from the back of my knee up the back of my leg to my buttock, so its kind of running up round to the outside of the leg.
I've continued running on it as it doesn't seem to be getting worse, and had a few days off for tonsilitis, however it hasn't disappeared.
Any ideas how to get rid of it/what's causing it?
Thanks
C