Trying to change my strings, I've been trying to take a bride pin out and the top has now broken off. What should I do? The string is stuck and I cannot remove the bridge pin
Take off all the other strings to gain access to the inside of the guitar. You should then be able to push up the broken bridge pin from inside the guitar. Use a small piece of wood to push with.
hmitchell730 First, cut off the strings, leaving about 2 or 3 inches above the pins. Then, get a good, fresh pair, of 'linesmen pliers' and try to push the strings into the guitar body. This is only gonna work on the wound strings, you can't likely grip the plain strings tight enough, and you might damage thee guitar trying.

Then, do what GM has suggested, push the pins out from inside the guitar.

Note: If you succeed in pushing the string stubs into the body, the pins will likely be loose enough to yank out from the top.

The string ball ends wedge between the bridge and the pins, causing the pins to bend a bit, causing them to bind. When you put your new strings on, bend a "J" into the ball end, ind make sure you get it under the bridge, out of sight, and toward the neck of the guitar. If you get this right, you shouldn't have any trouble the next time you change strings.
Just so I know for future reference, what make is the guitar? IMO, tight fitting pins are liability, and I can't understand why even makers like Martin persist in doing it. All mine are a drop fit, that is, I can pull them out with my fingers when the strings aren't under tension. When you do get them out, either make the pins smaller, or the holes bigger, or the grooves in either the bridge or pins bigger. 
If pushing the pins out isn't working and cranky's method of pushing the strings into the guitar doesn't work then you might need to get some needle nose pliers, reach into the guitar, grab the ball end of the string with the pliers and pull the strings out.  Once you have the strings out the pins should come out pretty easy.  If you do have to reach in the guitar with pliers take care not to pull on the pins themselves; you just want to pull on the ball end of the string.  Also be extra careful not to pull on any electronics if your guitar has a pickup.
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