If you have not logged on too many times (like 2 or 3 at most) you might be able to restore something from:
C:\users\USERNAME\AppData\LocalLow\IronGate\Valheim\worlds
and
C:\users\USERNAME\AppData\LocalLow\IronGate\Valheim\characters

You have two sets of files in each of those directories. One is your current game and the other is your previous game.
Look for files with your character's world-name and character name. One set of those will have the file extension ".old"

COPY YOUR CURRENT GAME TO A DIFFERENT FOLDER BEFORE THE NEXT STEP
Your current game has the same parameters as above, but without the .old extension
IF YOU HAVEN'T COPIED YOUR CURRENT GAME, DO IT NOW
Rename your .old files so they have the same name as the current ones (you'll have to delete your current ones, I bet- you copied them, right?)
There's a small chance your castle is in those old files.