Hello and welcome,
Colloidal silver therapy would not be safe for you; with your medical history and recent infection. Ideally a throat and phlegm / sputum culture with a chest x-ray should be performed, for the diagnosis. Following would be the treatment protocol for rhinitis / rhinosinusitis, meanwhile;
1) Nasal steroid; decrease inflammation and open up obstruction.
2) Oral decongestants such as pseudoephedrine are often helpful.
3) Topical decongestant for short duration.
5) Steam vaporizer
6) Eucalyptus oil may help
7) Nasal saline irrigation
8) Vitamin C
9) Antibiotics; only if culture is positive.
For treating it naturally; steam inhalation, nasal saline water (salt water) irrigation (can be done by Neti-pot), Vitamin C, Eucalyptus oil inhalation can be done. Following can increase the body immunity so help in overcoming the infection;
1) Omega 3; Fish oil capsule and flaxseed oil capsule.
2) Ginkgo Biloba
3) Zinc 30 mg.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.