I have a standing bike and there is a bolt that attaches the pedal's arm to the bike frame. I noticed a wobble while riding it and after tightening the bolt, it started wobbling again after a few minutes. I took out the bolt and the inside of the nut (and also the outside) looks rusted and the threads look like they are disintegrating.
It is not clear to me that this nut isn't fixed in place, but assuming I can't remove and replace it, does anyone have any advice on what I should do? Is there some kind of putty that I might be able to apply that will fix the bolt in place of some kind?
Bolt looks fine
Nut looks rusty (upper right hand corner). You can't see this but the threads do not look like they are in good shape.

