It sounds like it's more shaken up than in severe physical pain. Ducks try to hide their pain, though (however well they do or don't). I use herbs and natural medicine. I've had a duck with similar injury and have first figured what possible physical damage it could have recieved and given it the herb(s) to tend it, as follows:

Bone/Cartilidge Damage: Comfrey
Bleeding/heart (internal or external): Cayenne Pepper
Bruises/Pain: Lobelia
General Healers and antibacterials: Apple Cider Vinegar (raw's best), Garlic, Lobelia herb

(Note: Small doses for small things. They won't hurt to have a whole lot, but they might make it throw-up (lebelia is used for this purpose in too large a dose, and a little cures a lot.)

If you get these in liquid or powder you can mix it in her water dish and she'll drink it an be pretty well treated. Honestly I think your little ducky needs time, but sometimes the best thing to do is take the safe path in life and I'd certainly act via vet or home-remedy. I don't guaruntee the herbs will save your ducky, but it's just as guarunteed as a professional vet.

I use a formula called "Dr. Christopher's Super Garlic Immune", it's literally a cure-all. It has saved dogs from an "instantly" deadly poison, and several places from severe plague and disease. You might will to look up "Dr. Christopher" on google and get some of his formulas to have on hand. I'm not trying to be a salesperson, I just know they work and would love to see you have the benefit.