I usually get this when I haven't worked out for a LONG time and then I start squatting and dead lifting again. The last time I had it (I'm just telling you from my experience) I found that Ibuprofen and SLDL (stiff leg dead lifts) helped me as much as anything. Now whether that was in my head or what, I don't know. I just know the pain went away. Take that for what it's worth...
Also, foam rolling, or using a tennis ball helps. Look on youtube as there are some awesome stretches as well.
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