This is a simple procedure. All you have to do is drill out the pit until you reach the bubble, refill with pit fill resin and cure.

You can also remove the entire original pit fill, re-fill the pit and cure.  Most of the time you can eliminate this problem by checking the pit as soon as you apply the pit fill.  The bubble is usually already there and can be removed with a pick or probe.  If you keep your drill holes shallow you will have this problem less often.