Depends on the depth of the chip, polishing the glass could be possible to smooth it out. I've read of people buffing out noticeable gouges and scratches with cerium oxide but it takes hours and hours by hand, and still a considerable length of time with a powered buffing wheel.

Supposedly the optical properties of glass is very forgiving, and for the considerations of x-ray shielding and implosion resistance the glass layer of a tube's supposed to be very thick. I've never tried to do such a repair myself.

Quote Originally Posted by Gameguy View Post
When a windshield gets repaired, they add adhesive so the chip won't spread or get larger. The chip doesn't go away, and sometimes applying the adhesive can break the windshield as pressure is used to spread it into the defect.
Completely different application, windshields are subject to extreme temperature variations and the mechanical vibration of a car, plus the buffeting pressure of wind at highway speeds. If you can find a windshield/headlight repair technician bold enough to give it a try, you could probably bribe them into buffing out a defect in a CRT tube.