Not to worry, Presidents Harris and Biden will sort it all out.
No, seriously, this is unlikely to happen, but Nancy will not be up for re-election until 2022. So she will remain the speaker until the next Congress is called into session and they revote her in. If the election is not decided by then in terms of House seats, I think they go by vote for those who are in place, which I think is on December 1? Not sure… it's hard to find the exact info…