Nipple shields

So my baby is 5 days old today and while I was in the hospital I discovered I wasn't able to properly feed her. I have small and flat nipples which makes nursing super duper difficult. My nurse gave me a nipple shield and it literally saved me and my baby. The problem is that my nipples are so sore and they are starting to bleed. I don't know how to fix this since a nipple shield is my only option. Any suggestions?