She was sitting on my lap facing me and we were tickling each other. Suddenly we both leant forward at the same time and her head whacked into my nose. The bridge of my nose made a cracking sound 
It's pretty painful now (despite the application of a bag of peas) but hasn't bled. It feels very swollen; I can breath through it but it feels restricted.
Does anyone know how you can tell if you've broken your nose? And if so, can anything be done?