Rashes on newborn

Day 12 since our newborn arrived . Some one please tell me that it's jus a heat rash & nothing to worry . I am so worried . Each of my friends who visited him today said different things & am scared.

He has similar ones on his face & neck but Lot lesser than his tummy.

Also if it's heat rash can I apply homemade sheabutter - coco oil - calendula cream ? Or what else is the best for this ?

He is not running temperature or anything .