Dead pixels, need some advice!

OK so, I dropped my iPhone 6s on some very hard concrete, now its badly cracked on the left side. Then I saw there were some dead pixels near the bottom left of my screen. When I apply pressure on it, it spreads and when I remove my finger from the dead pixels it goes back to normal. I have 2 questions. What are some easy ways to fix the dead pixels? And if it spreads,(hopefully not) how long will it take to cover my phone in darkness?