Question about Topping

Like any open wound don't touch it and it will heal up and scar on its own. if you notice its getting infected chop below it and clear your tools. Don't spray it with anything. Some may wax it or tar it but its not a tree and its life cycle is under 1 yr so it will manage just fine. Next time when topping, do it when the growth is younger and more solid.

You could seal it with a little nail polish if your that worried. It'll just heal over by itself.

It will be absolutely fine, just don't fill it up with water or any other liquid. Cannabis has remarkable powers of overcoming adversity, topping being one adverse event. The hollow stub will dry up and shrivel down to nothing in time, there is no need to do anything, the plant will heal itself.

Yes this is called a disease entry point. This is a general horticulture problem and I would use another regular horticulture forum to address it for the best results.