Is it normal to be a little dizzy 2 days after a head injury that required stitches?

Yes. Some balance disturbance or dizziness can be normal following a head injury. Most patients will have complete resolution of symptoms with tincture of time. If still present after 7-10 days, you should see your primary care provider.
Abnormal. But not unusual. Take care, rest, analgesics mild, maybe ice to stitch area for a day or so.