This is a very serious problem because obviously, you bird needs his feet to stand on. As with any other problem, an examination by an avian veterinarian is necessary to find out if this is a medical problem - or to rule out a medical problem.
I there is no medical reason, you will have to find out why his feet are suddenly bothering him.
It seems that many birds who have this problem live with someone who smokes. We all know (or at least I hope we do) not to smoke in the presence of our birds, but not everyone knows that the nicotine left on your hands after smoking, may cause an irritation on your bird's feet. Soap left on the cage bars or perches could also have the same effect, but it seems that nicotine is the most common culpret.
If you smoke, please be sure to wash and rinse your hands thoroughly before picking up your bird. Nicotine is not good for people, so it is certainly not good for our feathered friends. Do not smoke in the same room as your bird or allow anyone else to smoke in the same room as your bird. Many smokers will only smoke outside the home if they have birds and that is a good rule to follow if you can.
Once you know what caused the problem, you will still have to solve it. Your bird's feet will have to heal and for that to happen, he may have to be collared for a short period. As with any mutilation or plucking, once he starts something like this, it becomes a habit very quickly and in order to heal, the habit must be broken.
He may also have developed an infection, which is a medical problem and should be looked after by your avian veterinarian.