Greetings, I am Dr. Pat. I have worked with birds exclusively for many years.
I am sorry no other expert has taken your question. We all come online at different times, I have just logged in and saw that you have not been answered. I hope I can still be of assistance.
Is the foot tightly clenched, or loose?
They can have nerve injury to foot, leg, hip or spine that results in a balled foot. Even very small strokes, metal toxicity,calcium deficiency and other things can cause this to happen.
Could he have fallen or caught his foot in a toy?
Can you tell me more about the bird?
How long has this been going on?
How long have you had him?
Where is he from?
Any accidents or trauma?
Interactions with other birds/pets/children/guests?
What is the usual diet? has it changed recently?
Has the bird gotten into anything? Chewed electrical wires?
If you feel comfortable with it, examine the bird thoroughly, using gentle restraint via washcloth or hand towel: do not restrict the chest or hold around the body. Check the eyes, nostrils, mouth and beak if possible, having a good look in there for mucus, redness, masses or anything else unusual. Palpate the tummy for pain, fluid, lumps or anything else (eggs, if female or unknown). Check all the joints for swelling, pain, and mobility. The feathers should be parted to view the skin, muscles and skeleton below; this can be done using a q-tip with isopropyl alcohol or KY gel. Look for bruising, lacerations, injured feathers.
Your job is to keep the bird warm, safe, quiet, and confined; and to provide adequate hydration and calories.
Move the bird to a box or carrier with soft towels in the bottom, no perch, and food and water in low bowls that can be reached easily. Put the whole thing on a heating pad on low or medium. Check it frequently, no overheating allowed! Keep the unit partially covered, warm and quiet. White paper towels or white cloth towels will show the true color of the droppings. Small animal/reptile boxes are great for this purpose.
The bird, bowls and unit must be kept very clean.
Here are some helpful links:
I know it is expensive, but you may not have many home options, because the first thing you need a vet for is to find out what is going on. Treatment is only as good as the diagnosis. If you call around, you may find a vet to work within your means. He might need radiographs, lab work, and pain management.
I really must stress that you need a bird-experienced person, and not just a vet who advertises that they care for birds.
You should take your bird to see an avian-experienced veterinarian ASAP for complete examination, diagnosis and appropriate treatment. Check
https://aav.site-ym.com/?page=basiccare click on "find a vet"