Breasts, self exam?

So I’m irregular and period comes ever 3-4 months. My nipples have been sore lately but I thought nothing of it until I was feeling around and found a small lump in my breast. It’s really close to my nipple. The lump feels no bigger than a marble. I have a doctors appointment on 6/27 but I’m trying to put my mind at ease. Has anyone ever had this before?