Can be normal. Black dots on a baby's tongue would most likely be due to some increased pigmentation. This can be considered normal and is usually found more commonly in darker-skinned individuals. It also can be considered hereditary. However, you should probably mention it to your pediatrician next time you have a visit, or if the baby seems bothered by it, have it checked out sooner.
See a pediatrician. It could be normal and not causing any harm. However, if uncertain it always best to see a doctor, just to put our mind at rest if nothing else.Good luck.
?diet. I have seen this from ingestible things such as vitamins with iron. Check with your pediatrician.