Hi welcome to the health care magic You are having periodic left sided chest pain.. Your EKG normal Hence no need to worry regarding cardiac causes Here pain could be simple muscular pain from abnormal sleep position or any unusual activity to which body not adopted.... You can be prescribed ibuprofen or Naproxen for five days Avoid strenous work for few days Avoid bad sleep posture while sleeping... If you are having any gastrointestinal symptoms like abdominal pain, nausea then gastritis like abdominal condition can lead reffered pain for which USG can be done for further work up Take care Hope your concern solved