Lump on toddlers head

My little girl was playing in my grandmother's house and tripped and fell right into the corner of the door. She has a big nasty blue bump right on her forehead and I'm wondering is there anything I can do for the swelling? She was lucky enough to be able to get checked by the doctor half a hour later and she said some painkiller and a cold compress but she won't sit still long enough to keep a compress on it. Any ideas?