1.
If you rub a substance in, you press it into something by continuously moving it over its surface.
When hair is dry, ~ a little oil to make it smooth and glossy.
PHRASAL VERB: V P n (not pron), also V n P
2.
If someone keeps reminding you of something you would rather forget you can say that they are rubbing it in.
Officials couldn’t resist rubbing it in...
The home side rubbed in their superiority with a further goal.
PHRASAL VERB: V n P, V P n (not pron)