Rescued bird not looking too good.

My wife and I rescued a pair of lovebirds from a terrible situation (they were kept in a small hamster cage with no perches for quite a while) The right side of this one is looking pretty bad, and his foot is swollen on the same side, he keeps chewing at it. He's still pretty active and is eating and drinking fine. Just want to make sure it's not an emergency considering it's a holiday today. Going to be taking to the vet soon but any idea as to what might be going on would be appreciated. Thank you!