OK to workout. You should still opt for a less strenuous workout to see how your body responds to be safe. In some cases, you might even help to reduce your nasal congestion and breathe a little easier thanks to your workout. Just proceed with caution and listen to your body if you struggle to breathe or feel more fatigued than usual.
The key is letting your body deal with your cold without prolonging it by running to the gym too soon. Sometimes rest is the best way to recover quickly and resume your workout regimen as soon as possible. When in doubt, always consult with your doctor to be as safe as possible because he or she will know your body and your overall health better than most!