M.M.
Ditto for Arnica Gel.
But you need to recycle the lactic acid, and if you're that sore, stretching cold muscles won't do a thing. At all.
So.
The squats/lunges..whatever you did to get this sore...do it again.
You need to do enough of the same exercise to get the muscle warm again, and get blood flowing through that area to get the acid out.
Then stretch.
Rinse and repeat.
It will SUCK while you do it, but get easier with each rep.
You'll feel MUCH better tomorrow. Promise.