This is a common hardware problem. I would suggest you go to any service centre to replace your phone screen. If the unit is out of warranty, you must pay for the replacement.
Unfortunately, the replacement cost for the original display will be higher. But that's the only solution.
Otherwise, reset your Galaxy device and verify if the problem still exists or not. But don't forget to get all the backup files before you do.
Use the steps below to perform Factory Reset on your Galaxy device. Go to Settings > General & Backup and reset > Factory data reset > Reset device > Tap Delete all.
Be sure to click the 3 dots and " ✓ Accept as Solution" when you find an answer that works for you.
