By now, I've learned two different words for being late: おそく and ちこく.
Now, I'm at a drill that asks for a translation of "Don't be late.", and offers both おそく and ちこく as options. The drill question was "___ しないでください。"
Naturally, I chose おそく, since it was the word I learned earlier and thus was more familiar with, but it was flagged as wrong.
So here's my question: Why is おそく wrong in this context, and ちこく right?