Nipple gunk? TMI nsfw maybe

Sorry if this is gross and TMI (I'm kinda grossed out myself). I'm 22 weeks pregnant but even before I got pregnant...sometimes I would like squeeze my nipple and this small amount of white gunk would come out. I always figured it was like lotion or sweat or whatever nastiness that had accumulated in my nipple. Now since being pregnant I can physically see it in my nipple hole but can't really squeeze it much like before cuz of the sensitivity from being pregnant but I can like scrape it away a bit. I'm wondering if it really is just sweat and bodily gunk (trust me I'm not a scumbag type person haha) or maybe part of the lactation process? I can't be the only one on here that knows what I'm talking about.