How soon can your nipples change once you've conceived?

Ivy
I was on cycle day 12 and my husband and I had sex using a condom and when we got done, we noticed it had fallen off. That was only 4 days ago but my nipple are tender and they are so dark they seriously look like they've been bruised. I have 2 children and my nipple got really dark with both of them and I figured this would be way too soon to see any kind of symptom but I googled it and found that your nipples can change as soon a s a few days after conception. I just was wonder your take on it! Thanks!