18 month olds teeth - one coming in behind another

[DaDaDa]

Our DS has around 8 teeth so far. A new one is coming in further inside the roof of his mouth, about 1cm inside another one.

Do we need to get it checked out by a dentist or doesn't it matter since it's only a baby tooth?

I think it would be best to check it out with the dentist, 1 cm sounds alot inside a little mouth.
Next time your going make an appointment for your ds and get him registerd aswell, if you haven't already.