Nugget is an apt Colonial military term to describe pilot trainees. Like many terms in the new Battlestar Galactica series, "nugget" is carried over from present day military slang.
Please note that "nugget" should not be confused with "rook" or "rookie." The later term applies to a person who as completed their training and qualifications, yet is still inexperienced.
Kara Thrace was assigned the task of flight instructor to train a batch of potential Viper pilots after seven were killed in a freak accident. (Act of Contrition)