I rinse my nostril 2 times a day with salty water for drainage will this cause infection.?

Distilled please. That's fine but there has been several cases of brain eating amoeba deaths in patients using nedi pots for sinus/ nose flushing with tap water. Make sure you use nothing but distilled, not tap water.
No. Using salty water or "saline" will not cause an infection as long as you use fresh saline and regularly clean the dispensing bottle.
No. Be sure that the saline solution is prepared in a steryl fassion and replaced regularly. If you do not use it for a few weeks then pour it out and start fresh. Boil some water for a few minutes and then add salt. Use this to rinse. You can also buy steryl saline at the pharmacy or market.