Most children who know how to fall asleep on their own will do so within 10 - 20 minutes of being laid down in bed at night. If your child is awake and playing long after you’ve said goodnight, it could mean your child wasn’t sufficiently tired at bedtime. At this age, most children need at least 4 hours of awake time before bed.
You can experiment with putting your child to bed slightly later each night until you find their sweet spot. Another explanation for lots of chatter and playtime before falling asleep could be distractions in their environment. Darkening the room and removing any toys from your child’s crib can cut down on the time it takes them to fall asleep.