Just hope it's not a bubble cause by rust under the vinyl... if it is - it's time to strip the top off and have the rust fixed ( it will just continue) .. then replace the top. If not - then as the fellow prior to me said - it's surgically slice and inject top glue behind the bubble and then press it and let it dry...

Inject with adhesive and press, provided that the vinyl hasn't stretched too far, may need replacement.