Boiling bass strings has to be the stupidest, most pointless thing I've ever heard of. I can KIND of understand trying to wipe them down with rubbing alcohol while still on the bass. But taking them off, the coiled, bent, fret dented messes they are at that point, and thinking 20 minutes in some 200 degree water is going to do anything to a nickel/steel string? And then you have to take the coiled bent dented up strings, that I guess at least are clean, except cleanliness is only one part of why they go dead, string them gently through your bridge, and then try to wrap them the exact same way around the tuners so they can have any chance of tuning stability. And then you're supposed to be able to get maybe a day or 2 out of them? Hellllllllllllllllll to the no.
As far as the pot, it's probably not "ruined", but it is f'ing gross. Like people have said, just get a cheap goodwill pot for 2 bucks and use that, or use that you already have that's kind of ruined for normal cooking, if you're intent on wasting your time.
Anyway, if your strings are rusty, just put the bass in a dumpster and quit music. Strings should never ever ever be rusty if you're remotely taking care of the bass. If you're not taking care of it, it means you dont have what it takes to be a musician.
I mean, youre here with rusty strings, and youre worried about ruining the pot by boiling the strings instead of saying "OMG my bass strings are rusty, how did this happen and how can I make sure it NEVER EVER EVER HAPPENS AGAIN once I put fresh brand new strings on, which I'm doing as I type this?" Quit being cheap and spend the 12 or 15 bucks for a new set, and before putting them on, give the bass a loving, thorough cleaning and tell it you will never treat it so poorly ever again. Then make sure you wash your hands before you play. Doesn't the poor defenseless bass deserve better?