Sounds like a blocked duct. Warm water/compress and massage it out (massage towards the nipple, not away). Maybe even try a bit of hand expression to encourage it to flow out. You need to clear it or it will turn into mastitis and trust me, you do not want mastitis! 😒
I'd make an appointment with the doctor just incase you can't clear it. But in the meantime try clearing it yourself. X

"Hormonal changes in the body can cause the milk ducts to become clogged with dead skin cells and debris"
It could even be an old blocked duct that happened when you were producing milk and is just getting worse over time. Your body is going through massive hormonal changes still as your baby is only 2 months xx

Sounds like a blocked milk duct to me, I believe that can still happen even when not breastfeeding. I would get yourself down to the doctors though just to get it checked over 😊 x