Thanks for your question, although I doubt that you will get this answer in time to help tell your boss what has happened. I recommend that you discuss your concern with your doctor
. Muscle spasms can happen anywhere in the body, and will often present as a tightness or other limiting sensation that tends to lock people in to certain ranges of motion. When this happens, it can take some time before the muscles relax and allow the normal range of motion to return. The core muscles, and other paraspinal muscles (or those that surround the vertebrae in our bodies) are quite prone to this sort of problem because of their delicate nature and the fact that they are infrequently used by many people except for in situations such as what you describe. Because of their central location, they can significantly affect mobility and cause problems for a prolonged period of time. While there are other things that can also cause the sort of symptoms that you describe, muscle spasms and cramps are one common explanation. Some people will have relief with over the counter analgesia, specifically anti-inflammatory medications, although any medication should be taken in consultation with your doctor and as per the manufacturer recommendations. Again, please speak with your doctor.