put my iPhone 7 into my teachers desk. “ THE SCREEN SHATTERED”

So basically I had to put my iPhone 7 into my teachers desk. “ THE SCREEN SHATTERED” anyway 2 weeks after it cracked, there were these black dots and color lines popping up on it . ofc I freaked out and didn’t know what to do so here I am waiting on an answer from you guys. Thanks for your time and I hope I get a response soon.