Originally Posted by
JohnDThompson
Often, removing the mounting bolt and riding around the block a few times is enough to work the arm loose. Don't go too far from home/shop, as once it gets loose you'll want to stop riding and walk back, or risk ruining the crank arm. There are kits to cut new threads into stripped arms; too costly for a one-off job, but perhaps a local shop has one.
Sounds like the crank arm is already ruined, but yes, loosen the bolt and ride. If a local bike shop has a tap to recut the threads, the crank arm might be salvageable.