breast cancer or just breastfeeding...

I’ll be calling my doctor tomorrow. I’m a FTM and I’m breastfeeding. Today I’ve noticed that a part of my breast is seems sunken in and it’s right next to a lump a little lower than my armpit. I’m up stressed, googling and crying thinking about breast cancer. It’s painful and I’ve been icing which helps some. It’s also warm/hot to the touch. Has anyone else dealt with this?

Update: I called the doctor and had my appointment this morning, it’s mastitis and they put me on antibiotics. Thanks for all the advice and calming my fears!