Is it okay if I blew white smoke in his face?
Why was there white smoke?
I was smoking a cigarette in the bathroom.
When you smoke you should mind people around you. It's rude to blow smoke on their face.
It's not like he/she/it can tell me off.
When or if they find out it was you, they will be very upset. You should confess to them and offer a sincere apology. Try to be more mindful of the people around you when you smoke and stand away from them.