All I can say is, get used to it! And maybe stock up on some tissues.
Many girls including me have experienced a 'big cry' that can come along, with release of all the pain, emotion and feeling from years of repression and dysphoria. It can take you by surprise and last a while. It sounds like you've experienced a taste of that.
And aside from that, welcome to being a woman.

Heck, I cry most days, over a variety of different reasons.