Does “nudziarstwa” mean something like “stupid humor” or “immature humor”?
Hello miketuholski 
Actually the therm “nudziarstwo” is already inflected - it’s Accusative as I believe. It would be “nudziarstwo” then and it could mean that something or someone is really boring, but truly I haven’v ever heard anyone useing this word. It is rather “Nuda” or you could say “Ale nuda” - “How boring”; “Jakie to nudne” - “It is so boring” - and etc. It’s much more natural.
If you have any other questions, I’ll willingly help you