It's normal for your nipples to feel a bit tender in the beginning (it shouldn't last long), but if baby is latched on properly (i.e., deeply), your nipples should never blister, crack, or bleed. If they DO, you'll need to help baby learn to achieve a deeper latch (she should be taking in a good chunk of breast, not just your nipple). Breastfeeding shouldn't be painful. Get hands-on help to ensure baby gets it down pat…and that you don't suffer nipple damage.
In the meantime, rub a drop of breast milk on the surface of your nipples after each feeding, and let it dry. (Seriously — it helps.) You can also try wearing hydrogel pads (like these from Ameda) for a few days while your breasts heal. They'll soothe your nips and provide a moist, healing environment without leaving a slippery residue on your nipples like some ointments and creams. (The slip-sliding has potential to keep baby from achieving that great deep latch.) If your nipple is wounded and shows no signs of healing, starts looking super shiny and bright, or you begin experiencing severe pain and flu-like symptoms, head to the doctor. Bacteria may have gotten in, which can result in an infection such as mastitis.
And remember: Let your nipples get some air when possible, change your nursing pads often, and never clean your nipples with alcohol or soap (just stick with plain water).