We haven't had any real young with splayed legs in. Ours have all been older and were too late to do anything corrective. I have spoken to a vet about it in the past and it is attempted at times to "hobble" the legs to make the one straighten usually this is only the case if it is quite minor such as just sticking out a bit at an odd angle. Sometimes while the chick is still young the leg will be broken or dislocate by the vet only and then wrapped to heal in the correct position. Other times the leg will continue to be splayed in either case and can't be corrected depending on how badly splayed it is and how young it is when it develops.

Either way on a young budgie (to end a run on answer) yes my first attempt would be to hobble it but check regularly to make sure it is not effecting circulation by being too tight or pinching nerves or blood vessels, even loose wrappings can sometimes effect blood flow and even cause nerve damage if not done correctly. If it does not seem to be working at all within a couple weeks then the only option would be a vet or to just work with training a handicapped budgie. The older ones we get in never act handicapped and get along quite well. Good luck