Is it normal to only be able to wink one eye?
Mostly.Normal for most people
Yes. Lots of people can wink with one eye but not the other; it usually comes down to natural differences in coordination and practice.
That’s a normal little body quirk. Winking takes a bit of coordination, and one side of your face may be easier to control than the other. You can try practicing the other side, but there’s no need to make it a project.
If this is a new change and you’re also noticing facial drooping or weakness, get medical advice promptly. Otherwise, one-eye-only winking is generally harmless.