How long can I use cracked screen?

I had the notion one day that my Speck safety case was causing the speakers to not be loud enough. ( it's still very hard to hear and people hearing me ) Anyway, I went in the house with a handful of things, and of course, as soon as the phone was out of the case. Splat. Fell right on its face. The cracks run from top left to center right. The only odd thing I see is a small pale yellow circle, about the size of an eraser on a pencil. I just wonder if this crack might damage the phone or if it's only an aesthetic thing? I got an iPhone X, but sent it right back because of the lack of a home button, too much swiping, but the camera was great and the little perks. So, I'm back to my iPhone 6 - cracked screen and wondered. Can I live with this or am I slowly damaging my phone? If it were to be repaired, take to where? Apple Store?