Anyone had it before?

Yesterday I had a real bad pain at the back of my knee that went down to my calf and up my thigh a little, sort of felt like an achy/tight/cramp feeling and was painful to touch. Now today I have the same pain/aching just under my butt and also on the side of my foot, all on the same leg- feels like a trapped nerve or something- and I have a rash of tiny blisters behind my knee.

Also been real tired and feeling like I’m coming down with a cold for the past few days, but didn’t really think they were related until I saw the rash.

Will be calling the doctor in the morning but just wanted to try and get an idea of what’s wrong before heading in.

Thanks!