My nipples were the first sign of me being pregnant with my son. I wasn't trying so it took another week or so for me to realise what it was, but yeah it's hard to explain they were just very sensitive (and not the way they get around PMS or ovulation, it was different but again I can't explain it) and they used to get so cold.
So it could be a good sign, I'll keep fingers crossed for you
This has also happened with my two bfps! Sounds promising, good luck!