Thanks for writing in,
It seems you are suffering from simple muscle spasm. A course of Muscle-relaxants + NSAID's will relieve your spasm and pain along with physiotherapy
in the form of IFT (Interferential therapy). Apply hot water fomentation over the painful site twice a day. Take rest on hard surface. Avoid prolonged sitting, leaning forward, lifting heavy weights and traveling for a week.
Get well soon,