Welcome. Assuming you've tried everything normal, such as tapping lightly from the side, or James suggestion. Some collets loosen, then get tight, and have to be loosened again to release the grip. If you do get the bit out, if you used any force, I would no longer trust the collet. Have you checked ereplacementparts.com? Don't run bits their full depth of the shank, you want them to have then end of the shank about an eighth of an inch shy of bottoming out. I use a half inch grommet (not an ering) to keep bits from bottoming. I have never had a bit stick.