Q: There is a greyish thin line appearing on my screen

Hi Blas1997,

Welcome to the Support Communities!  The resource below explains what to do if you see you see a line on the display of your iPhone:

Get help with the screen on your iPhone, iPad, or iPod touch - Apple Support
http://support.apple.com/en-us/HT203039

If you see lines, missing sections, discoloration, or poor image quality

 

1. Try to restart your device. If you can't restart, reset your device.
2. If restarting or resetting doesn’t fix the issue, restore your device.
3. If you still see the issue after you restore, contact Apple Support.

I hope this information helps ....

- Judy