You should definitely go to see your primary care doctor
about this issue right away. The symptom of weakness in the arm after lifting something very heavy is concerning for potential shoulder injury
. Your doctor will be able to examine your shoulder closely looking for signs of injury and help you decide what to do.
The shoulder is very susceptible to injury, especially with heavy lifting or repetitive motion. By far the most common form of shoulder injury is damage to the rotator cuff, which are a series of tendons that surrounding the shoulder joint and control the muscles that are involved in lifting and rotating the arm at the shoulder. The tendons in the rotator cuff can either be strained or outright torn. Your doctor can tell if there is damage to the rotator cuff by looking for pain or weakness at the shoulder with specific arm movements. They can also rule out other less common types of shoulder injury, such as a shoulder dislocation.
Based on what your doctor finds, the may recommend simple treatments, such as ice and anti inflammatory medications, or if the injury seems more severe, they may want to get radiographic imaging of the shoulder to further define the injury.