It can really hurt on some people, while others it doesn't.
I've been on HRT for, um, almost 3 years (I can't remember) and I still sometimes get that. I got it at the start, then it went away -- and now after being post-op I've been getting it again... I have no idea when my breasts are going to stop growing. I just wear sports bras now 'cause none of my bras fit (and half of my clothes, as my hips came out, and my body still changing).
So, anyway, your body is going to change and it can be painful (my hips hurt when they started going out... oh, did it hurt, growing pains all over again). So, with change sometimes people get more pain than others.
good luck!