I know this sounds crazy, but I once rescued a little mouse from my cat's mouth, and he too had a leg issue and wasn't walking. I guessed that it may be broken, so I took a toothpick and broke off an end, and taped it to his leg with medical tape creating a splint. My husband (at the time) thought I was off my rocker, but it worked! His leg healed and I am sure my home made splint helped.
Also, my cat once had a weird thing happen to his leg. I never knew what exactly happened, but he was limping around with his front paw lifted, but not all the way off the ground, so it was dragging. My vet (who is the best vet ever!) said that there was apparently some sort of nerve damage and that if he continued to drag the paw, it would get scraped and infected, and so we needed to consider amputating it. Well, I asked him if I could wait just a couple more weeks, to be really sure it wasn't going to get better. He said yes. I went home with that cat and every night as he slept next to me, I would massage that area, and VERY carefully, uncurl his paw, little by little each night. Within 1 or 2 weeks, his paw had completely straightened out! Soon he was walking on it again as if nothing ever happened!
So don't panic about little Chubnut. He may just heal and have a limp. My neighbor has a goose that has a severely deformed wing and he lives a perfectly happy life. I've also seen a deformed Blue Jay come to my feeder that cannot walk right. He lives in the wild and does just fine. So have faith, you never know!