petty
n.n. caring too much about small, unimportant things. You use this to describe someone who gets angry or makes a big deal out of tiny problems.
n. unduly concerned with trivial matters, especially in a way that is small-minded or spiteful. Often used to describe behavior motivated by a desire for minor revenge or a lack of generosity.
It was petty of him to complain about a five-minute delay.
The neighbors have been involved in a petty dispute over the height of their shared fence for years.
While the policy changes were significant, the debate in the boardroom remained focused on petty grievances and personal slights rather than the future of the organization.
Typically used to modify nouns like 'dispute', 'argument', or 'behavior', or as a predicative adjective following 'be' or 'seem'.