Hey bro. I copy and pasted this from another thread where I wrote on the same subject. Just so you or anyone else with this problem know its not all doom and gloom. The cannabis plant is very resilient. Hopefully yours recovers fine. Here you go.
Hey guys. I just wanted to share some of my experience with broken stems. I do a lot of LST work, and have broke my fair share of main stems. I had this one that broke almost completely. I mean, I'm serious, there was like a thread of fiber holding this stem together. Guess what I did to fix it. Nothing. I actually assumed it was done and just left it there as is. I wasn't even sure if it was female at this point. You know what happened, it completely healed itself. It regrew a new stem from the thread that was left! It became a thick little knuckle looking knot kind of thing, and none of the plant died or suffered. It blew me away.
Because of that, I did this same thing on purpose to a sativa that was stretching too much. It was on the edge of the garden so I decided to experiment with it. I did the same thing, basically broke the stems so they were barely hanging on, and it did the same thing, just repaired itself. The stem will be bent permanently, but since I was laying branches down for my LST work it worked out perfect.
Definitely interesting.