I'm not seeing any botrytis... the dead twig and larf are just that - dead. They might have had their stems pinched so they couldn't get water up to the leaves or something but this does NOT look like bud rot at all.... the first sign, for ME, of bud rot is a completely dead sugar leaf in the middle of an otherwise healthy looking bud.... this is entirely different.
I wouldn't worry about it, tbh, and no, cinnamon wouldn't do a thing for that fungus anyway.... you would have to spray the cut you made with a 2% alcohol solution, sterilize all utensils and your hands and then get on to inspecting every single bud on your grow.... You're pretty damned close to harvest now anyway so if you're really worried about it, just inspect your harvest VERY closely and wet trim it so you KNOW you've inspected thoroughly... but honestly, I don't think you have anything to worry about... (and I lost my entire summer grow to botrytis last year... it's painful!).
Good luck...