What Causes Strain And Numbness In Neck?

I was stretching with my arms behind my back and my head down and suddenly there was an intense pain my my throat it felt like the left side of my throat under my chin popped inward, when I moved of tried to swallow there was a sever pain. I forced myself to swallow soon after and it popped back in place, there is still a weird strain when i swallow and that side of my neck feels weird and numbish. What happened?