Fussbudget noun US informal, old-fashioned.
(UK fusspot)
a person who is often not satisfied and complains about things that are not important: "I can't eat this meat - it's too tough." "Stop being such a fussbudget and eat your dinner!"
(Cambridge Dictionary)
Fussbox is another AmE variant:
(Southeastern U.S.)
a fussy or needlessly fault-finding person Also called: fussbudget
(Collins Dictionary)