Its not possible. The only effective way to get rid of a bunion is with surgery. Exercises may help keep the joint mobile and help with some of the symptoms inside the joint. A bunion corrector will also help with the symptoms and may help improve the angle of the big toe by a bit. Manipulation and mobilization of the joint can also be of some benefit. Obviously wearing better fitting shoes is going to help as well.
There is nothing “natural” that you can take or rub on a bunion that will shrink or get rid of it. If you did Google, ‘how to shrink bunions naturally’ you will find an extraordinary amount of nonsense that will not come close to helping bunions. If you do not believe me, then just try some of the suggestions and see how it works out for you.