I won't ask how you managed that, as I have done dumb things too.
You can try an easy out tool, I have had limited success with them especially on smaller screws, bolts. Another option would be to drill and tap the bolt that is in there, be sure to centre punch. once you have it drilled use a bottoming tap and with permanent thread locker screw a bolt into your broken bolt, let the thread locker cure and back it out.
Good luck.