Survivant depuis 2012
12 years ago I went through the exact same thing. I found a small hard lump next to my areola. It was about the size of a pea. It didn't move around much -- I actually tries to push it in all directions but it pretty much stayed put.
Now, I'm sure you know that the majority of breast lumps are not cancer. There are cysts, fibrosis, and a number of other non-cancerous things it could be. Mine happened to be cancer. I strongly suggest you get it checked as soon as you can.
You don't mention how old you are, whether there's breast cancer in your family, and other such things. But it doesn't really matter. You need to have it checked soon. There will probably be several different things they'll want to do, which may include a mammogram, ultrasound, needle biopsy, surgical biopsy. (These are in sort of sequential order.) It's better to be safe than sorry.
Best of luck to you!