A lot of things happen when you start keto, all at once. One of them is that accumulated crap comes out. While it may be annoying and a nuisance, spontaneous sinus drainage is better than getting infected. Been there, done that and it was one of the most traumatic experiences of my young life. Six months of weekly visits to a doctor to have my sinuses ‘pressure washed’. I’ll take the runny nose over the alternative any time. Rest assured that something you can live better without is going away. Keep the end of your nose lubed to prevent drying. Chapstick is good.
Also, cut the carbs to sub-20 grams per day - not ‘close to give or take’. The lower the better. Ketosis is a healthful state and you want to encourage, support and remain in it consistently, especially when just starting.