If you were injured at work, talk to your doctor. Tell your doctor about all the symptoms that you are still experiencing. If you are recovering from a Missouri or Kansas on-the-job injury, you should listen to your doctor's advice. If your doctor says that you should not to work because to your injuries, then do not work - even if your employer is pressuring you to come back to your job.
You can ask your doctor for an off-work slip or medical excuse. Tell your boss that your doctor has told you not to work and show him an paperwork from your doctor. Companies are not allowed to force workers to return to work after an on-the-job injury until they have been cleared for work by their physician.
After an injury, your doctor may initially release you to work on a light duty or a restricted status. If this is the case for you, ask your employer if they have a position that fits your restrictions.
Your boss can not fire you for following your doctor's orders.