What could sore nipples mean??

My nipples are a little sore today.

I am on the pill, and I have been for 3 years. Next week is my placebo pills/ period.

I normally don’t get tingly sore nipples so I’m a bit concerned for the reason.

I am sexually active but I am on the pill...

Any ideas on what it could ? Possibly pregnant ? Just because my period is next week?