If you refer to a person or thing as a tiddler, you mean that they are very unimportant or small, especially when compared to other people or things of the same type.
[British, informal]
On a world scale, the earthquake was a tiddler.
tiddler in British English
(ˈtɪdlə)
noun British informal
1.
a very small fish or aquatic creature, esp a stickleback, minnow, or tadpole
2.
a small child, esp one undersized for its age
Word origin
C19: from dialectal tittlebat, childish variant of stickleback, influenced by tiddly1