is your neck sore? on the opposite side? I know that sounds crazy, but I recently had a pinched nerve in my neck and one of my syptoms was the same warmth you're describing -
My neck has been a bit sore - at the point where the neck meets the shoulder but I think it's more a shoulder pain than a neck pain and it's on the same side.
My hamstring on that side hurts when I run for the last day or so but not when I do dead lifts.
I always have a few aches and pains from the gym so it's hard to know what is muscle soreness that will pass in a day or two and what is related...

Maybe I should just see the Doctor, I can nag her about my other trivial issues at the same time.