Quads, glutes hurt when stretching hamstrings

[Sierra]

This seemingly popped up out of nowhere.. when I attempt to do a hamstring stretch now, I get a lot of stiffness in my hamstring (but no pain, just inflexibility) and pain in my quad & glutes. It's gotten to the point where I cannot stretch my left hamstring if I wish to stand up afterwards. It's mostly only in my left side, but my right side has started seeming a little off too. I looked up some stretches to isolate the quads/glutes, thinking they had just tightened, but I did those stretches very easily with no pain. I tried just resting, that didn't really make it any better.

The only thing I can possibly connect this to is an incident with a horse which involved me landing quite forcefully on my back.. I had back pain for a week or so but it went away, and the glute pain replaced it.
I don't know what caused this, or what I should do to fix it.. I don't really think it's an injury because it doesn't bother me when I'm on land, it only comes up when stretching, skating, or doing one-foot squats.. input?

[Doubletoe]

The tightness in your back resulting from that fall could very well be the culprit, forcing your quads to work harder to pull your body forward in the hamstring stretch when they encounter resistance from your tight back. 
My back is tight on the lower left side and I used to feel a strain in my right hip flexor whenever I stretched my right hamstring, but that went away once I changed my stretching method to reduce the strain on the hip flexor and and quad.  I started doing my hamstring stretch with my lower back flush against the wall, placing the palm of my left hand on the wall behind my lower back and pushing myself forward that way instead of pulling myself forward with my abs, hip flexors and quads.

I'm not sure if the glute pain is some sort of referred pain from your back, but that's possible, too.  Another explanation is that what you are feeling is a strain on the top of your hamstring, where it connects to the top of the femur right in your glute area (feels like it's under the middle of your butt cheek).  When I pulled my hamstring, that's exactly where I felt it and that's what my physical therapist explained to me.  We had to do lots of deep stretches to work through some scar tissue I had right there.

I'm not a physical therapist or doctor, so these are only guesses based on my own personal experiences.  

[Sierra]

I tried the wall method, and I could see my quad still tensing. I worked on it for a few minutes and managed to push down a bit without tensing my quad. It still hurt a bit but not a lot. Partly it's my hamstring, too, it feels pretty inflexible.

That's where I feel part of it, too. I looked up pulled hamstring symptoms.
*Swelling/bruising- don't have any of that
*Pain when extending or fully flexing leg- nope, I can kick my foot up to my butt with no pain
*Pain when running- not at all. But I did get a lot of pain just stroking and doing crossovers when skating.

Since hamstring is supposed to be an extension of the lower back, perhaps they are just a little sore and stiff from the back injury. It was a pretty hard impact- right afterwards, and then an hour later, my vision blacked out and I got dizzy. I'll just rest for a few more days, with just gentle stretching, and see how it feels. I've been stretching out my back a lot too.
Thank you