Hi!
Before looking into replacing any component check the connection between the LCD panel and the motherboard. You might have not inserted the screen ribbon cable or the screen power ribbon properly. I suggest that you disconnect the screen and plug it back in. Also while at that, check the screen ribbon cable for damage, anything like small dents and/ or bending signs could damage these fragile ribbon cables.
If you find nothing and reseating all screen connections does not fix your issue, replace the screen.