Gouldian Finch favoring one leg

I have a pair of Lady Gouldian Finches. one has a orange head male, female has a red head. I have had them for one month. the female laid one egg, after a week threw it out of nest. Now male is favoring one leg. I don't know if female injured him, or could he be getting sick.

I feed finch food, millet sprays, greens, treat seed, grit on food. I also use vitamins in water. They sing beautifully. I try not to stress them. I woke up one night and heard a lot of noise coming from cage. Male holding on to side of cage panting. Seemed like they were fighting or mating.

Now he stays in nest. I gave them nest to sleep. I don't have to breed. If they fight and hurt each other, will his foot heal? His foot is not bleeding. Does not look discolored.