If you continue to have the orangish-brown mucus, you really need to have this checked out. It could be a fungal infection.
Most likely this is coming from one or more of your sinuses. It can be an infection or simply an inflammation that is not infected. There is also a good possibility that this is the cause of your 4-month cough. Having a CT of your sinuses might be a good idea. I would speak to your doctor about sinusitis. Sinusitis is an inflammation of the mucous membranes that line the sinus cavities. Inflammation of the sinuses could be due to an allergy, an infection, or ongoing exposure to an irritant, such as pollution or smoke.
it sounds like you might have sinus irritation on that side and post nasal drip......do u have any pain on that side? u should drink lots of water and blow your nose well to clear the mucous to prevent infection which you may already have............good luck
UPDATE: Woke up this morning and things are back to normal...just kind of freaked me out because I've never seen that color mucus before and couldn't understand why it would only come out of one nostril. Thanks for the help!