Worth separating singing from night frights before you go further, because the fix is the opposite way round. A night fright is a panic in the dark: thrashing, crashing into the bars, and tiels are badly prone to them. You can lose a blood feather that way.
If what you hear is actual song, carry on. If you ever hear flapping and banging, put a soft light on, talk to him until he settles, then check him over. Birds that fright do better with a dim night light than with total darkness.