24 weeks noticed lump thing on boob

Last night I was changing clothes and I rubbed my hand across my breast right here and noticed a spot that wasn’t on the other side. It does not hurt at all, it’s on my RIGHT upper middle of my breast, I noticed today when I wore my sports bra it got bigger feeling (may just be me freaking out) but now tonight it’s back to feeling small and I can’t see it like I could this morning in this picture.

I have an appointment with my OB on Tuesday so I’m getting checked out then but just wondering if anyone has had any kind of similar experience? And if I should worry.,,