He ate Vaseline!!!! Did you see a doctor?
One of those bizzarre things children do. Netmums have an online 'clinic' with lots of posts about children eating things ranging from petfood to sudocrem to mud, generally the end advice is always the same LO may end up with upset tum for a couple of days, if there is any violent reactions (severe vomiting/breathlessness/severe diaorrhea) then take to A&E with sample of what they've eaten.
Hopefully LO is no worse for wear. Best wishes.