BF help!

This is my second child and I don’t know how my nipple got a cut that is deep. She has a good latch but it is so painful and won’t heal because when she BF the cut reopens. I dont want to end BF early but feel like quitting due to the pain. I’ve been supplementing with formula during the day and giving her one of my boob. The other boob feels so dry and feels like it’s going to get a cut too. My LO is 2 mos old. I noticed she has white stuff on her lips and it’s on her gum and I’m not sure if it’s thrush but would this cause my nipple to crack? I am taking her to the peds tomm. I’ve been applying breast milk, lanolin, bacitracin too my nipple. Would a nipple shield help? Please help this is so stressful and painful. There’s no white thrush on my nipple just very dry, crack and you can see the cut 😒