I think it really depends on where and how you get bit! I have had some small nips from Cocoa, but they were either "testing" or "warning" bites (when she was young and my hand was new to her she occasionally gently nibbled me, or if I do something she doesn't want me to do eg. trying to pick her up when she has something in mind) - these were never really painful, just enough to make move my hand away.
I imagine when your brother was bit the hamster was panicked because of the stuck foot, which would result in a more painful bite. These can hurt quite a lot depending on the spot! But to reassure you - in the past I had a hamster bite that drew blood and I don't recall being in a lot of pain from it.
I know it can be a little scary but if you patiently tame your hamster and you two get used to each other, I don't think your hamster will bite you unless in an exceptional situation!
Cocoa gave me a lot of nibbles when I first got her and she was testing the waters, but in just a month or so she got really used to me handling her and now she only ever bites me as a warning, which is never painful.