Have you tried nasal saline solutions?
Repeated neti-pot saline solution treatments might help lessen the bad odor.
It could be a stubborn infection of the sinus, where the mucus might be degraded and causing the bad odor. IDK.
What have your doctors suggested and what have you tried?
A steam treatment with essential oils, like Eucalyptus essential oil (organic)might help.
Just put a few drops of the Eucalyptus oil in a tub of very hot water and cover your head and tub with a lg towel and inhale through the nose all the steam you can for as long as you can- safely of course. Repeat often.
I hope it helps, however, please note that this is not intended as a replacement for medical advice.
This could be a nasal polyp or a foreign body. You need to see an ENT specialist and have yourself examined properly.
I would try to clean it frequently and get checked by a skin dictor if it is your nose its coming from, also tro to cover the odor, out mask it.