Think I screwed up topping my plant.

So I have two plants that I know are male, and since I'm killing them ASAP anyway, I decided to get some experimenting practice in on them and topped one. I cut the plant on the top node just above where the fan leaves hit the stem. Pretty much right after that the cut looked black, it's been three days and nothing has been happening at the site.

Did I screw up?

Will try to get a pic up ASAP if nobody knows from description.

Try cutting 3/4 of the node and always use clean tools to cut