Sounds like it very well could be muscle strain. If it is, it can take time to fully heal, possibly several weeks.

You might try some heat to the muscle to see if it gives you some pain relief and either ibuprofen, or aleve for pain as well.

If it goes on for 2 weeks without any relief or if you have any numbness tingling or burning along with the muscle pain, I would suggest that you see your primary doctor.

Those symptoms would indicate a more serious problem with your spine than just a muscle. Something like nerve compression.

Fran

As you've been in pain for at least a week, you should probably seek medical advice either from your doctor or another professional such as a chiropractor. They should be able to advise on the root cause of your problem and recommend treatment, exercises and prevention advice.