I just replaced my lcd , i noticed that everytime i touch the screen there is a white dot under my finger and it follows my finger where ever i drag it. I dont know if they screen is bad or if its a tracer put on by the previous owner. The screen works fine other than that problem
Is Developer Options enabled on your device under Settings? If so then check and see if the option for " Show Touches " is enable under Developer Options. This would do as your saying and show a mark, white dot, etc. where ever you touch the screen.