grow into

verb2

1. •
   To grow in size, so as to be able to fit (something, especially an item of clothing).

   • His new jumper was a bit big for him, but he'll grow into it in a couple of years.
2. •
   To become accustomed to (something) by maturing.

   • At first, the new job as managing director was way over my head, but I grew into it.