I think greenfrog has a good point. Seeing a professional for help now will be valuable. You can discuss what to do if this depression persists. You may learn so valuable skills and ways to better identify the level of depression.

One thing to keep in mind is that concussion can cause a flat affect. How flat affect fits with depression is hard to know. Understanding this issue may be helpful. I get very frustrated by the flat affect I experience.

My best to you.