Some people would advise putting it down (take it to a vet for them to do it, feed it to a larger lizard if you have one). Others would say that if there's any way the gecko can have a decent quality of life, even if it needs to be hand fed, you should let it try. The yolk sac will eventually fall off. It's hard to tell without seeing it if its jaw will allow it to eat or not. If the jaw won't allow it to eat it will die soon anyway.