It is possible that you and your baby have thrush. Look in you baby's mouth and see if you see any white spots or areas. Baby's tongues are often white just because of the milk, so look at the inside of her cheeks and lips. Beware, though, because you may have thrush even if your baby doesn't have the white spots. Unless your baby is not latching on properly all of a sudden, which would be unusual once nursing is successfully established, there is no reason that you should be sore.
I had thrush with my second daughter, and I didn't identify it for a long time, and it was MISERABLE to clear up. It escaped diagnosis because she didn't have any white spots in her mouth, so when I asked her pediatrician and he didn't see anything, I just dealt with the pain until it was impossible to ignore. I thought I was latching her on wrong, and by the time my sister-in-law (a doctor) looked at my nipples, they were cracked and bleeding.
If it is thrush, you need to see her pediatrician or your doctor. In my case, the first step was to prescribe Nystatin to paint on the insides of her mouth and on my nipples. I also used anti-fungal creams on my nipples, let my breasts air-dry in the sun (the sun kills yeast), and sterilized all bottles and breast pump parts. I had to do all of this for a month, and when it still didn't work, they finally prescribed me an oral anti-fungal medicine that I can't remember. It cleared it up in 3 days!!!!
If you've caught it early, you shouldn't have to go through all this. Learn from my mistake, though. Unless you think you might be sore from your daughter latching on wrong or if you've been bitten, it might very well be thrush. DO NOT tough it out. The sooner you treat it, the better!
Good luck!!!!!!!