A pulled arm muscle may feel very sore, with a sudden onset of pain and a limited range of motion, states Healthline. The arm may feel weak or stiff, with apparent bruising and discoloration. The area may also swell, have muscle spasms or seem knotted up.
Pulled muscles are also referred to as muscle strain, according to Healthline. A muscle strain that is mild to moderate may take weeks to heal, but a severe muscle strain can last for months. Often, mild-to-moderate muscle strains require physical therapy, and in severe cases, surgery may be required to repair the affected muscle.