iPhone App Shows a white light dot when the iphone is woke up from sleep mode

I am not sure whether this is a strange case,but this is the scenario.

1. I open my iPhone app in my iPhone device and i work on the app

2. I Lock my iPhone device and I try to unlock the pho开发者_C百科ne from sleep mode

3. When the unlock is successful, I see a white light of size 3 to 4 pixels in the center of the screen and from that point the app resumes.

What would be the reason for this error, kindly help.

This didn't happen after a specific amount of time - no clue why it came up.