There are reasons that you would have a muscle ache without actually having injured a muscle. Most of the time this type of thing goes away fairly quickly. When it doesn't go away, some of these causes should be investigated. First, it is possible that you slept on your arm wrong causing some muscle pain
. This usually goes away in one to two days. Many types of infectious such as the flu can cause muscle pain as well. However, these illnesses usually also cause things like fever, chills, cough and other symptoms that go along with the muscle aches. Another possibility is that you have developed a problem in one of the joints of your arm. Problems with the joints or tendons and ligaments associated with the joints can cause pain that feels like muscle pain. Finally, certain medications especially those used to treat high cholesterol can cause muscle aches that are not associated with any injury.
I suggest that you schedule an appointment with your primary care physician
. He or she can take a more detailed history of your symptoms and perform a thorough physical exam. Depending on what your doctor
finds, you may require some blood tests and possibly some imaging of that arm. Good luck.