They need to step in and either HR or the boss needs a come to Jesus meeting and you can explain exactly what happened and apologize for the error. And state you’ve already done so with the desire to move forward from an honest mistake.
Your coworkers have created a hostile work environment. Say those words to HR and I would be shocked if they didn’t take immediate action. I truly hate when adults act like children. HR needs to shut it down and even explain to all about hostile work environments. If it continues—HR can and will force your boss to deliver corrective action.
Good luck. I hope things get better.