For context, DS is 4 weeks old and feeding him as been totally pain free for about 2 1/2 weeks. I'd imagine each baby feeds differently, so I dunno if my story is any use but:
First of all, pinch and tug on your nipples, hard. It's not exactly SORE, is it? But at the same time, it does make you wince a bit, right? That's the first way I can describe it. I also had quite flat nipples (don't any more, now they point!) so I imagine that my baby had to do quite a bit of sucking to get them to point enough for him - and that was probably some of the initial pain, for me. If I'd know about them at the time, I'd have worn Breast Shells for the last month of PG.
Secondly, DS had a tongue tie and so couldn't latch properly. He did end up sort of rubbing the skin off my nipples in the first week, and there was a bit of red sore skin (who am I kidding, it hurt like hell) - thankfully I never saw blood in his mouth/my milk, or I think I would have had a meltdown.
Thirdly: what saved my breastfeeding relationship was that I got help within a few days of coming back from the hospital. Basically: home from hospital on Friday, weekend spent crying, wondering if I should FF, posting on MN in a state, and getting chewed on the nipples. Lactation consultant to my house on Monday. It was expensive but we'd saved up for it, and that visit (plus her availability over the phone all the next 2 weeks!) has made the difference between me continuing to BF or switching to formula. She taught me how to feed lying down, which didn't hurt the already-sore parts of my nipples, and she recognized that DS had a tongue tie. I got that snipped in the next few days - and then could feed sitting up again, cos (1) the sides of my nipples had had time to heal and (2) DS could now latch and not slip off and chew.
The last week feeding has been a breeze - I've fed in waiting rooms, on a park bench, in a sling, in a bar (mmn, burger and a beer with new mum friends!) at mum's groups, on a bus.... but I wouldn't have got there without a lot of help, tears, and a fair bit of ibuprofen and paracetamol. It DID hurt. Lanisoh is great, so are their 'soothies' (gel pads for sore nips,) - but I can now tell the difference between the deep 'tugging' sensation of him latched on well and feeding like a leech, and a bad latch that is razoring my nipples and must be stopped AT ONCE! I'd say if you're worried about it (and I was!), get really good help lined up now now now, and be willing (if you can put the money aside) to pay for someone to come to your house and stay with you and your partner for a couple of hours, and show you lots of different ways to feed. Of course, you might have someone in the area who will do that for free, or a place you can take them the first week where you'll get help - I didn't have that option, so had to pay for immediate help. We're not very well off and paying for the lactation consultant was hard for us, but it was less than 2 1/2 months' worth of formula costs... and BFing now is a doddle. I can hardly believe how hard it was in the first week - but I can also see why so many mums stop, and wish they hadn't. If we hadn't had a LC come round, I think I would have stopped, no question. I was just so worried that I was starving DS, and being in pain myself made me question everything. The deep pulling on the nipples isn't painful (though I've yet to find it blissful!) but the lacerating pain of a bad latch is bloody awful, AND you don't need to put up with it. .
Gawd I've written an essay. Sorry! Good luck and enjoy your gorgeous new baby :)