(its not colostrum, unless you've got a placenta attached to you somewhere. we can't reproduce the exact prenatal hormone cocktail that would cause colostrum)
It could be milk eventually, but its likely not that. before you ever get to milk you're going to release duct fluid. that's likely where you are and its perfectly normal. So long as you aren't penetrating your skin with the needle its probably just normal prolactin-derived duct fluid. even less to worry about if its bilateral.
with flatter nipples, its fine. more breast, same amount of nipple means the nipple can get flattened a bit. do keep an eye on it because if it starts to point inward, specifically if just one points inward, that could be a thing to bring up to a doctor for concern of breast cancer. tons of people just have inverted nipples normally, i kind of used to at one point before NBE i think. but yeah.
You're fine~
-Aria