Hard knot above left breast/under creases of both. Is it common to develop lumps/knots 9 months after breast reduction/lift?

I noticed a hard knot/lump above my left nipple that is causing me concern. I feel other lumps/knots along the crease of this breast as well as my right breast. How can I tell the difference between a lump that can develop after a breast reduction/lift or something more serious? I have an appoint next week to see my PS who specializes in problem breasts. I have a mammogram scheduled for tomorrow at the local hospital.