Weird feeling during 90-90-Stretch

Hi folks,

for those of you who don't know the 90-90-stretch, check it out

Left side is fine, I feel the stretch where it should be.
But once I switch to right, I get a burning feeling where the hamstrings are and can't even get far enought to feel a stretch without extreme burning pain!
(The skin even becomes very touch sensitive, a slight touch produces burning sensation)

Any idea what the hell is going ong??
Thx!