By "nuts", does he swim back and forth really really fast?
As long as he's not crashing into the tank, it's fine.
My betta does this every single day. He seems me, and swims up to the side of the tank I'm at and swims back and forth, back and forth, back and forth (because he's excited).
I put my finger up and he stops. Why? He thinks I have food, whatadork, hahaha. It's normal, this is how I love to play with them. You set up your finger, they stop. You move it, they follow. You move it back, they follow back. It's a great way to play with them . He's just paying close attention to your finger.
Only one of mine doesn't do it, because he's too busy swimming back and forth for food, haha.
He's not stressed, he just wants to play (or so, my case is). And I still don't think it's ick, lol. Ick is more 3-d and sticking off of his body, rather than flat little white spots. But they do tend to look like salt and/or sugar.