Working with glass on a daily basis, that happens often. Really only way is to pry it open and either squeeze it out or pull it out. Unfortunately, that cut going across, you can't get the best squeeze without more damage IF there is still glass in there. Sometimes I've had to use my utility knife to open up a cut even more.
Only other thing I can recommend, torniquet the finger, pull open the cut, use tweezers. You'll probably need a helper. It sucks, but it works...I know from personal experience.