Ahh, the joys of object throwing.
There are days when my 30 month old empties the kitchen drawers and throws things around. Why not? They make great sounds, sometimes bounce, and mama runs around like a crazy person trying to keep glass objects from shattering and metal objects from clanging.
It is tough because you really can't have a "no throwing" rule because it is okay to throw some things in some places.
But we do have a "no throwing at the mama/papa/cat/baby brother" rule and
I do have place rules like "no throwing in the kitchen" and object rules, "no throwing plates".
But it is a game, so if I am around I stop the action and say in a crazy mama voice "oh there's no throwing that measuring tape in the kitchen" and then ask my son what he can throw. Sometimes he has an answer that is acceptable or I will feed him one. "Yes! We can throw the ball down the hall or yes, we can throw the elephant in the playroom. So then we act on it. And make a biiiigggg deal of doing it. I throw wildly and then he does it and it's fun and he practices his skills and it's all good!
You will notice they will start to make their own rules with silly voices. My son would run in with a plate and say "throw the plate at the cat? Noooo!" and then he'd give an alternative idea and we'd run down the hall and do it.
We go outside and throw orange peels when we are peeling our oranges or throw socks at each other when folding laundry....
He will get it! I promise...just redirect and state a rule and then go let him throw something!
It isn't fun, but this too shall pass! Good luck!