The LCD panel in the lid got damaged. Likely along the edge so som e of the lines got severed. Sadly this will require a new display assembly [product|IF301-002-11] iFixit only has the Rose Gold in stock. Here’s the guide to put it in [guide|104756]
Here’s a run down on the Apple P/N’s for the different units:
* Gold - 661-02248
* Space Grey - 661-02266
* Rose Gold - 661-04852
* Silver - 661-06786