After psilocybin, many people feel tired yet wired. Psilocin can keep 5-HT2A signaling elevated and boost glutamate in the cortex, which raises arousal. REM latency may be longer and early deep sleep can be lighter, so sleep onset feels harder. Melatonin is not directly blocked, but its cue is often outweighed by this cortical activity.
On top of that, the sympathetic system can stay active and slow the needed drop in core temperature that helps trigger sleep. The Default Mode Network is also re-stabilizing, which can feel like ongoing mental processing.
What helps: keep lights low and screens off, breathe slowly with long exhales, try a brief warm shower and then a cool bedroom around 16 to 18°C to aid heat loss, and keep stimuli minimal. If you prefer gentle, non-pharmaceutical ideas, see these natural options for better sleep.
Be patient; as your system settles, sleep usually follows.