PECCADILLO: FLAW ::

Peccadillo is a term used to describe a minor fault. The given words are synonymous. The second word is a bit severe in degree as compared to the first one.
'Clandestine' means to do something secretly. Clandestine and openness are antonyms. We can eliminate option A. 
Forensics is used to refer to the team that preserves evidence and analyzes them. The function of a judiciary is to hear and judge cases. We cannot establish a relationship between the 2 terms. 
An invasion means to attack a country from outside. A Putsch is a term used to describe a coup. The 2 terms cannot be said to be synonymous. 

A 'nick' is a term used to describe a small cut or a small quantity. A 'score' is a term used to describe a cut or a scratch on the surface. Therefore, option B is the right answer.