This happen to my cockatiel this morning! What was the outcome for you?? :(
If you know of an avian vet ( that's a vet who specializes in the care of
birds) that would be your best bet. We have a pet male cockatiel as well.
If this happened to our bird, you better believe I would find an avian vet
and I would make an appointment for him with the avian vet. You said
you gave your cockatiel medicine left over from your other cockatiel.
You have to be careful doing this. That medicine was for you other bird
not for your current bird. You have to be careful that the medicine hasn't
expired. Bandaging his leg may make this worse. If he fell off his cage,
he may have other injuries you're not even aware of. He really should
be seen by an avian vet.
If it's just a bruise, yes it will heal on its own just as our bruises do. Is he able to bear weight on it at all? Are all the toes still in proper alignment? Is he able to flex his foot, open and close the toes? If he's able to do all these things, there's a good chance he doesn't have a break. But only an x-ray will show for sure. And if a digit is broken, the vet (preferably and avian vet) will do the proper foot wrap for him to keep the toes in proper position till the bone heals.
If you can figure out how he may have fallen or caught a toe on something, that would be great so you can change things around so it won't happen again. I hope it's just a bruise and he heals quickly.