red and blue thin lines at the middle of the screen

my phone have red and blue thin lines at the middle, i dropped it earlier but i only noticed it after maybe 4 hours because it is very thin and only visible at dark colors like black, my phone is ok but the problem started when i noticed the lines, i can't type the letters on the middle, i can't touch everything on the middle and everything just freezes but when i pressed the lock button it become okay again but started acting up again after 1 hour or so then i pressed lock button and it become okay again until today but i'm scared that it will happen again so please help me.

update : when i touched the screen the lines will appear but when i'm not the lines will fade not totally disappearing, there's no problem but i just want to get rid of the lines