TMI- nipple color change?

This may be a little tmi, but I am 11-12dpo and I just noticed that my nipples look a tad bit darker than usual kind of like a super light brown when Usually they are very light pink. It’s not a huge difference but enough for me to notice. I also noticed that the nipple it’s self has a white circle dot in the center that’s very noticeable. Im on my 4th Cycle ttc baby #1. I also haven’t noticed this any other time before (but I’m that doesn’t mean it hasn’t happened). Could this be a sign of conception? I tested this morning and got negative but AF isn’t due until Saturday so I plan to test again in a few days.