My baby has a hard bump on the back right side of his head. i've read that this could be a bulging fontanelle, which worries me. should i be concerned?

Wrong position: The fontanelles are located in the midline, one in back of the forehead & rarely a 2nd just in front of the back of the head. A bump on the right side back would likely be a blood accumulation from birth trauma if large and a lymph node if small..

Bruising ?: The anterior and posterior fontanelle are both midline, so if the bulge is posterior and right sided, the likely cause is some form of scalp bruising, most likely cephalhematoma, if a hard bump. Your only concern should be jaundice, not brain damage, as this scalp bleed is not intracranial, or within the skull, it is more superficial than that...