Re: Bending bones!
I don't think asking someone to do something a bit differently because it's hurting you needs to be such a big deal or embarrassing -- and although in this case it's just bruises so not that big a deal, personally I think it's good to get in the habit of feeling confident and relaxed about speaking up, and someday in the future it might save you a preventable injury or accident.
Of course sometimes we choose to go through pain because we feel like there's something useful we're learning or for some such a reason, but other times it's just pain and nothing useful enough to justify it, or sometimes it gets in the way of learning, or presages an injury about to happen. And in any case, it's purely up to you to choose when you want to go through it, it's not something you need to just get sucked along into by default.
I..e, I would try not to think of it as wimping out... try to think of it as standing up for yourself.