Replace…what? You should really finish your sentences.
Replace it with a new one. They’re like, what, $12? Your only other options are to get it re-tapped (which will cost more than $12) or super glue that sonuva gun.
Are you sure? Did you flip the axle around and that other side went in fine? Did you note thread damage to the side of the axle in question? If those are true, then yes, new axle. Go to hardware store and look for set screws.
Yeah…no offense…but that’s really no help unless you know what “something” is. Like If I said " I know the secret of the universe! It is…something. Sorta like trolling…