Therapist + writer here
Trauma is a response to an event. Not the event itself.
You might have heard of PTSD (Post-
traumatic stress disorder), which is common amongst veterans (but keep in mind -
not all veterans experience PTSD). A lot of time those symptoms can include hypervigilance, insomnia, nightmare, loss of interest in daily activities and/or isolation. There are also triggers that might "bring them back" to the event. Examples of trauma can be big like Hurricane Katrina (T) or small like watching a parent fight (t).
When someone experiences trauma, there is a separation. A disconnect (they can be dissociated = emotions brain separate from the logical brain). Remember that it's someone's response to an event.
Not all stressful event leads to trauma.
Moving forward with your story, you should identify what happened exactly. What are your MC's responses. Then think about impact of the trauma. And the consequences (aftermath) of living through that event. Think how it plays out psychologically. Emotionally. Physically. Interpersonally. Financially. Spiritually. All the lys. How does the MC recover from trauma? How does it affect relationship? How does it affect self-esteem? Well-being? Body image? Trust with others? School? Work? How is the MC recovering and what are the obstacles they are facing?
As writers, you are essentially a "mini-therapist", really diving into the MC's psyche and ultimately, writing the story on how they keep moving forward.