Flush out the sinuses with a neti pot (available at all drug stores and many health food stores, sometimes large supermarkets). Add a pinch of salt (and some people say a pinch of baking soda) to warm water. Follow the directions or ask the pharmacist - it's pretty simple, just do it over the sink. It feels weird and you will feel extremely full (if you already have an infection, the pressure might be uncomfortable but it passes as soon as the water drains and your blow your nose).
Sense of taste and smell can absolutely change. Post nasal drip and clogged eustachian tubes affect taste, and of course the sense of smell is all messed up, partly from the congestion and partly (sometimes) from the odor created by the bacteria.
You may need antibiotics to clear this up - I'm not sure - BUT you can do a lot through nutritional supplementation to prevent future infections. I used to get them periodically, and a friend of mine got several infections every year. I have had nothing since, and he has only had 1 in 11 years. If you don't like drugs, there is another way.