Breast lump?

I recently stopped taking birth control pills. I was on them since 2012 then switched to IUD in 2016. I switched back December 2019. However my doctor recently found that I have incredibly low estrogen levels despite being on an estrogen pill. She wanted me to stop taking it so we can retest and see what my body is producing on its own and whether the pill might have been causing it somehow. I stopped the pill about 4-5 weeks ago. Almost two weeks ago I noticed a lump in my left breast. It’s hard and painful to the touch. I know most lumps are benign and go away on their own. And since I just stopped the pill I figured that had something to do with it. But it isn’t going away and it still hurts when touched. What could this be? At what point should I see my doctor about it? My follow up appointment is in 3 weeks. Would it be okay to wait that long?