I fell yesterday and hit the front of my head
Local inflammatory swelling...
The area of the scalp and forehead is highly vascular. Injury here leads to increased bleeding as well as increase inflammatory changes. The swelling you noticed is most likely the results of inflammation and subcutaneous bleeding. I would recommend you to ice the area and start antiinflammatory medicines (ibuprofen). If it hurts severely, it would be worthwhile to get an examination.
The swelling in the picture looks abnormal; but not unusual for injury in this location. So I would not be overly worried unless the pain is severe and intolerable.
Hope this helps. Let me know if you need clarifications.