Hello EleanorRead,
Windows Hello Pin is linked to the Windows Device where the Microsoft is signed in, therefor a Windows computer where you can sign in in order to reset your Hello Pin.
In a case or urgency you can use Microsoft Teams web through: https://www.microsoft.com/en-ww/microsoft-teams/log-in or if a link for a meeting was shared with you you can always log in as a Guest.
--If the reply is helpful, please Upvote and Accept as answer--