Look here first:
that might help.
My totally unprofessional, uneducated, unsmart opinion is that they are hemangiomas. What did they doctor say they were? He is right... if they are indeed hemangiomas, they will go away. The going away part is called "involution." I don't know they will go away that quickly... no one can really predict that.
Has he suggested any treatment options and how old is the baby now?
In this case, "treatment options" might include doing nothing unless they begin to grow very fast. So, if he has said "wait and see" and is continuing to monitor them, that might be OK.
Other parents will chime in soon, probably. Welcome to the board!