When to start toughening my nipples?

Jocelyn • I am a vegan lesbian in rural New England pregnant with our first child. TTC'ed for 9 months
Hi all. I'm 8 1/2 weeks right now and my breasts and nipples have been hurting for weeks. I got cold yesterday and the hardening was agony! I'm not worried about the pain - I know it's normal, but my MIL is insisting that I need to start doing things to toughen my nipples for breastfeeding right away or I'll regret it. She's telling me to start using a toothbrush on them. I cringe just thinking about it. I was planning to wait until the second trimester before working on toughening to see if my breast soreness will die down a little, but I don't want to miss out on bonding time because of pain when the little one arrives.
When did everyone start working on this?