No, you don't have to hire an Accountant. You can remove the "R" for reconciled within the account register of the account you need to re-reconcile. If there are "many" transactions in the register and it would take a long time to do this, you can use a different email account to create a "QBOA" (QuickBooks Online Accountant) account, then send yourself an Accountant invitation. Once accepted, you can act as your own Accountant and "Batch Undo" the account reconciliations under the briefcase icon (Accountant Tools/Reconcile/History by account/Action/Batch Undo) for Accountants in the QBOA account login.
Ps: Also, I am an Accountant, and I do not charge my clients to "Undo" account reconciliations for them when they choose to do their own account reconciliations and need to redo them.
Log back into your regular QBO account and send yourself an Accountant invitation to the email address you used for your QBOA (Firm) account. Then go to that email account and accept the invitation. Then login to your QBOA account and go to your client list, you should be there as a client (Your Practice/Clients). Select your regular QBO client. Then go to "Reports" and "Reconciliation Reports", this will take you to the same screen as the Accountant Toolbox method.
Just creating the Accountant login (QBOA firm account) is not enough. You have to invite yourself as an Accountant under your original QBO account so you can access that account as the Accountant under the firm account. Make sense?