Option 1:
Take the cross threaded bolt out and toss it.
Buy a new replacement bolt, and buy a tap and retap the hole, to clean up the threads.
CAREFULLY install the new bolt - It will be VERY easy to cross thread it again.
Option 2:
Drill out and retap the hole to the next size up.
Option 3:
Drill out and get a new, longer bolt with nut and use as a through bolt in place of the tapped installation.