Football Language: Niggle
This term can be used as a verb, to niggle, and adjective, niggling, or a countable noun, a niggle. However, in football it is most often used as an adjective when talking about a kind of foul or injury or as a noun when talking about an injury. A niggle is defined as a trivial discomfort or annoyance, so if a player has a niggle, it is a way of saying they have a small but recurring injury. The injury could be described as a niggling ankle injury, which means the player has a problem with their ankle that will not heal, get better, quickly. You may also hear the phrase niggling fouls, to describe a situation where one team is committing a lot of small fouls, and therefore disrupting the other team’s rhythm.
Example: Emre Can pain-free after niggling injury and happy to stay at Liverpool (headline from the Guardian, 13 March 2017)