My screen is starting to go black where I chipped my phone's glass

I have had my S8 for around 1½-2 years now, and I am more than pleased with the phone. Recently I cracked my phone pretty bad, and with that some of the glass chipped off in the top right hand corner of the phone. Around a week ago, I noticed some of the phone’s display turning black up in that same corner of the screen. Assuming that's what is happening, how do I prevent it from happening anymore to the phone? I would like to maximize the time I have with this phone as long and cheap as possible.