If anything just make sure you dont have and really hard lumps that stick around. In all honesty they should feel like a balloon with cooked oatmeal inside. Squishy with a little texture but they have form. A good way to check is to either spiral out from the nipple ending in ur armpit or go over your chest in a grid. The main thing is to walk ur fingertips with a tad bit of pressure to feel for any defined lumps. Check once a month, and if you do find an abnormality keep an eye on it and make sure it doesnt hurt when prodded or stay for more than a few days. If it does either, talk with your doctor. Because your boobs are starting to grow they’re gonna be pretty lumpy. Breast tissue is lumpy. It shouldn’t be very hard or pebbly they should be squishy and kinda springy. Also dont freakout too quickly when there is something that feels out of ordinary since your boobs are still growing thats gonna happen. If the anomaly sticks around, then you may want to talk to your doctor.

Tl;dr version: feel all the boob, if there is an overly tender bit or pebbly bit that sticks around uncomfortably long (more than a few days) talk with your doctor.