I've had every breastfeeding problem ever, multiple times, so I feel like I can weigh in on this!
Do you feel a lump anywhere in there?
It sounds like a clogged duct, which are really common, but can lead to mastitis. If you get mastitis, your doctor will need to step in.
I often got clogged ducts when I was engorged and/or when I went too long between breastfeeding sessions.
To help, nurse your baby frequently. Take warm/hot showers and massage the sore areas extensively toward the nipple. Even though it hurts, keep massaging. Also - hand express in the shower. Those are the only things that have ever helped me with a clogged duct. Pumping didnt help because the pump was not as strong/efficient as my baby's little mouth.
If you start to feel achy all over, get a fever, or see a wedge shaped red mark on the outside of your breast, head to the doctor. That means it has developed into mastitis and you will need medicine. Take this very seriously.
I DONT think it is thrush, because that normally affects the nipple first, and then moves into the breast, and is INCREDIBLY painful when you nurse.
Good luck, mamma!