I never felt nauseated during breastfeeding, but it does create quite a rush of hormones when the milk lets down and I have heard of this effect. My daughter experienced this for a few weeks early on. And nausea is fairly common when related to other hormone changes, like starting or changing birth control pills, and when we get pregnant. This sensation will probably fade in coming weeks.
For extreme nipple soreness, do yourself a favor and try nipple shields. My first weeks of breastfeeding were intensely painful, with nipples so raw they would bleed. Nipple shields during nursing for several days really turned that around.