Rhinitis flared up with sudden weather change from hot to cold. now the right side of face is very congested, ear is plugged, right-sided throat pain from post-nasal drip and headache but mucus is clear? is this just inflammation and swelling?

I would suggest Nasonex or similar preparation in Brazil (steroid inhaler) to reduce the congestion and acetaminophen or ibuprofen for pain and headache for a couple days. If symptoms do not abate or clear mucus changes color, you may need oral antibiotic for bacterial superinfection.

Yes, you may be dealing with inflammation &swelling from infection in the m,axillary sinus. If mucus is unable to drain out of the sinus you won't see discolored mucus. Inhaling steam,applying heat to your cheek & saline nasal spray may allow drainage to flow. Your MD can prescribe appropriate antibiotic if he/she agrees with the diagnosis of acute maxillary sinusitis