PostEaseAct on what you can still control first
If any access remains (a linked email, a connected device session, a recovery option), securing it immediately is the priority. Every major platform has its own dedicated account-recovery and hacked-account report flow; searching the platform's own current help resources for the specific process is more reliable than following generic advice, since these flows change.
Warn your audience through a channel the account itself does not control
Since the compromised account may be posting on the attacker's behalf, warn followers through email, another platform, or a website update. Anything outside the hacked account's control reaches people faster and more reliably than trying to post from an account you may no longer control.
After recovery, review what let it happen
Once access is restored, reviewing connected apps, active sessions, and whether a strong, unique password and two-factor authentication are in place closes the specific gap that allowed the compromise, rather than restoring the account to its previous, vulnerable state.