Yes, it is possible they are dried out grafts that did not take. They may be lost grafts that may not grow. Some may also be scabs. It is always a good idea to follow up with your doctor.
It is safe to remove the scabs after ten days you shouldn't pull out forcefully but may be after the shower when try are a bit looser play with them with your finger tips and they will start to fall off.
Stem cell is still under investigation and research. There may be some doctors that offer it in some countries but the prof that it works has not been established yet .