Eight herniated discs here, two BIG surgeries, can no longer be "fixed" & am now disabled. DO NOT DO stretching of any kind on a "new" injury. Use ice to reduce swelling for 3 days. 20 min on -20 min off, as often as you want. Try Ibprofen or Aleve. You can go up to 3-4 ibprofen, every 4-6 hrs. This is a prescription dose(600 to 800 mg total). With Aleve, you can try 2 Aleve every 12 hrs max.. After 3 days you can try heat. Moist heat is better. It will loosen muscles somewhat. Think relax in a tub of comfortably hot water & read a quilt mag. You can now try alternating the hot & cold treatments. This might speed up the reduction of swelling. Do no bending, twisting, lifting etc. It could be more then a pulled muscle. If it's not better in a few weeks or gets progressively worse or instantly worse, see the doc!!. I could tell you more put this will get you started. Take care, be careful!! & I hope it's just a muscle & goes away quickly! (Started for me at 17 & am now 59 so I've spent most of my life dealing with this).