Thanks for writing. If your plant has started to rot, the best thing you can do is let it start to dry out again. Making sure it's in a warm, bright spot can help it recover more quickly, as can good air movement. If your pot has drainage holes, make sure there's not water sitting in the saucer --- and if the pot doesn't have drainage holes so excess water can escape, transplant your plant right away into one that does.
---Justin, Senior Garden Editor, BHG.com