The Quiet Ones (2014)
By Draco Malfoy,
A university professor and a team of students conduct an experiment on a young woman, uncovering terrifyingly dark, unexpected forces in the process.
During the course of it she digs at her thigh with a bobby pin. I think it was fairly graphic– blood on her leg and face etc.
Edit: the trivia section on IMDB says she also stabs a safety pin into her knee, with blood not shown. I didn’t remember that.
Also I think she has one or both arms scarred from a suicide attempt. I did hear her say “stop staring at my wrists” at one point but wasn’t looking up.
Movie Title The Quiet Ones