Hi there, my hair was ombré (brown to blonde) and I put a chocolate brown over the top only to have parts of the end turn a weird greenish colour. Is there anything I can do without going to the hairdressers? Would a toner work?

No,a toner won't work. Go to the hairdresser if you don't want to look like a clown.

A toner wouldn't work. You need a red additive to balance out the green. If I were you, I would go to a salon where they professionalize in color corrections.