What should I do?

Some child smashed your phone into the ground after you let them use it to call someone? That is ruthless...

Unfortunately the A series Galaxy devices are cheaper than the flagship models as they have cheaper components... except for the screen. The screen is usually the most expensive part to replace on phones and this one is no different. If you can find a cheap part supplier that will have good quality parts, the repair itself isn't too difficult if you take your time, and you don't have much else to lose in terms of the devices value, so give it a go. Otherwise if you've got important data you may want a repair shop to extract it for a cheaper fee and move it onto a new device.

I’m still wondering for what reason that kid would have done that…