I think if I were to get bitten by a larger fish than I have in any of my tanks, I would be worried.
When my bettas bite, it doesn't hurt. The only time I've ever been bitten by a betta and it scared me was when my sister's bettas were in a divided tank, and they were trying to attack eachother through the plexiglass, and i stuck my finger in to distract one trying to break them up and he turned around and but me and hung on. I had to shake my hand very roughly to get him off. I was afraid I'd hurt him.
Also, I was moving a decoration around in my 10 gallon sorority, and my biggest girl came up and bit me on my elbow, which surprised me, but it didn't hurt. :P
Other than that, I have a 6 inch cichlid and 3 large tiger barbs who will come and nibble at my finger if I stick it in their tank, but they're piglets and they think everything is food. lol.