Armpit lump

Hi there. I'm 37 years old with a painful lump in my armpit. I'd guess the size of a peanut M&M. Maybe a little larger than that. It's somewhat firm like a grape but seems to move around. It's smooth, oval and tender. It can be felt somewhat on the surface with gentle pressure but the size can't be truly determined without deeper palpation. I can't really feel for where it ends underneath.

I noticed very significant pain in my entire right armpit a week before my period that resolved before my period started. That's not unusual for me. I used to have a problem with that in my 20's and my right arm pit particularly. In fact, I have breast tissue in that armpit that has always sagged. More so around my period. It even filled with milk and caused a lot of pain after my pregnancy 8 years ago. I didn't want to panic about this but I didn't even know I had this lump. I'm 4 days into my period and there's a pinching pain in the lump. Possibly because I'd been touching it. I'm ashamed to say that I don't have a habit of checking my armpits for breast exams. I've always had a tendency for pain in my right armpit occasionally for a few days before my period but it always resolved enough for me to assume it was hormones. Notably, painful breast and armpit tissue has been less of a problem over the last 5 years compared to my 20's. I was surprised that I was having as much pain as I was this time. I randomly decided to check for a lump and there it was. I was really only sometimes noticing pain at the predictable times before my period and was shocked to find a lump. Now I feel pinching sharp pain when I touch it and a little bits of shooting pain when I don't touch it.

I don't recall feeling pain beyond PMS anywhere in my armpit before this cycle. I didn't feel any sensitivity or anything when I shaved or washed the area before this cycle. I have a feeling the lump was there though.

My mother passed away from breast cancer at 46 years old. I had a breast biopsy years ago for a fibroadenoma type mass. I've had numerous cysts but nothing lately. I checked my breasts and don't feel any masses. I had some cyclical breast pain a week ago before my period along with the armpit pain that resolved. Covid fear has prevented me from seeing a doctor in over a year.

I've seen a few people mention the armpit being where their cancer was first discovered and that it was painful.

Is it reasonable for me to wait one more cycle before making an appointment? Is there a anything reassuring about what I've described?

Thank you so much. Hugs and support to you all.