That really stinks.
Unfortunately, one of the things they don't teach you in nursing school
is that once you train up to any role (charge, preceptor, etc.) it is very hard to step back down if you no longer want to do it. There's such a limited group of people with these specialized skills that it's way easier for your managers to just keep you around. You're either 'voluntold' to keep doing it, or given a serious, ongoing guilt trip if you request not to do it anymore.
There really isn't much you can do, and we can't know how sympathetic or petty your senior manager will be about your decision. If they've changed your status with HR, it's totally within their rights to tell you that your bedside position is 'no longer available' to you; in that case, they can simply refuse to put you on the schedule and continue to schedule you to fulfill management duties. If they really won't budge on this issue, maybe you could look for another job to start fresh without any management expectations. Regardless of whether you stay or go, if you're worried about bad blood affecting recommendations I'd look for another nurse in the unit who is more sympathetic to your situation and can write one for you (a former preceptor, a charge nurse, etc.)