If medical management in the form of topical corticosteroids, decongestant medications don't help, then diagnostic nasal endoscopy should be considered. It's a OPD procedure, so accurate findings of involved sinuses can be obtained, which helps in further planning.

This is easily remedied nowadays by a minimally invasive procedure called Balloon Sinuplasty where a balloon catheter is introduced into your normal ostium and inflated. this unites the accessory ostium with the normal ostium which drives the secretions forwards, so you can blow it out if your nostrils onto tissues when you have a cold. Subsequently, your doctor will put you on appropriate nasal medications including nasal washing regimen to gradually heal the sinus infection or inflammation. You are welcome to visit me in Bangalore where I can do this for you.