The light should not be associated with sleep. I think this is a learned behavior that he has picked up over a few months or years. It's best to start relearning that behavior. I advise parents to avoid any time of screens 2 to 3 hours before bedtime. Because bright lights or blue light suppresses melatonin and the child's sleep is delayed. The first thing we need to do is reduce the access to the screen for him. I'm not sure what age your child is but I suggest removing screens from his vicinity and introduce a different space for him to sleep.