Sounds like you strained a muscle or muscles. Most likely quadratus lumborum or one of the erector spinae muscles. Fascia connects muscles to eachother which may be why you tilt your head and feel it in the calf- or more likely the insertion of the hamstrings which may have also been traumatized.
How to expedite healing? Stay out of the gym and take it easy for awhile. If you are still working out, its probably not that serious and will most likely heal on its own. Ice it after workouts.
As long as you dont have "shooting" "radiating" pain from your low back down your ass and leg, its not nerve related. If you do, it could possibly be a disc herniation, which consequently, compresses the spinal nerve root.
Just let it rest a few days and ice it after activity.