I've been nipped by Dionysus so many times, but it's never actually hurt me. Of course, I have cats, a dog, a bird, reptiles, and have handled untame HAMSTERS(OUWW!) so a fish bite is like...nothing! XD It did 'hurt' worse than the baby garter snake that got me, but neither of them broke the skin or anything like that, it was more of a surprise.
If a betta fish was koi sized, THEN that would hurt!