I had a young duck who had a leg problem a few weeks ago - very swollen, limping very badly (to the point of barely moving). I got her into the vet as soon as we noticed (husband had been in charge for a couple of days and hadn't noticed her) but even then it wasn't clear if it was broken or not. She could put some weight on it so we thought not. Vet prescribed a week of anti-inflammatories to help with the swelling and pain. I kept her isolated by day in a big dog cage with a carry case in side and she pretty much sat in that with food and water close at hand (but I'm sure she did lose some weight). Then I let her back in with the others each night - partly because I thought she was a bit exposed to foxes in her cage - even if they couldn't get to her, they'd have bee close enough to scare her - and partly because she missed them all (much shouting went on!) .That didn't seem to work so I phoned up and asked what else we could try. Vet was happy to try antibiotics in case it was a joint infection. The only problem was that his preferred antibiotic was not ideal for such a young bird (she was about 2 months at the time) but the second choice was great and within another week she was up and about again. So it clearly was an infection.
Fingers crossed yours is not a break but, yes, get her into the vet tomorrow,
H