Wait a little while and then try stickers on the potty.
A few years ago, a coworker mentioned to me that her 2.5 yo daughter was going thru a worrisome phase in that everything was frightening to her... like the light switch, the smoke detector, the electrical outlet... etc. And her daughter was freaking out, screaming and crying, refusing to go to sleep, etc. My coworker was at her wits end. I suggested that she call the free mental helpline that our health insurance offered... The "experts" suggested that she and her daughter pick out/buy stickers together and every time that she said something was scary, to put a sticker on it and see if that made it less scary. And it worked-?! (I know, it sounds so simple!)
So, a few months ago, my two year old started to refuse to use her potty. She had been ok with it and then, just suddenly decided against it... So I asked her why she didn't want to use her potty. She said it was scary. So I found her mickey mouse stickers and over the next 3 days, she plastered stickers all over her potty, especially the lid. And voila! She was comfortable with using it again.
Worked for us. Maybe it will help you...