A "stickler" is someone who insists that everyone follow the rules. You can express what kind of rules the stickler makes people follow with the phrases "stickler for ___" or "stickler when it comes to ___":

My boss is a stickler when it comes to correct spelling and grammar.

She's a stickler for punctuality.

The correct preposition to follow "stickler" is "for", but sometimes people use "about":

I'm a real stickler about keeping the kitchen clean.

The word "stickler" sounds a little negative, but it's not rude or offensive.