hi friend! i'm transmasc so if i'm overstepping by replying to this thread i really apologize, but, when i still had a lot of breast tissue i also had a high tendency to experience what are called "fibrocystic breast changes", which are benign and happen due to hormone shifts but can make areas of tissue feel lumpy/hard. that might be what's going on there! it's also not uncommon for fibrocystic areas to feel sore or tender. really hoping that it's that or something else similarly normal/benign for you.