My toddler got a bump and cut on his head. How should I treat it?

Wound care. If the cut is superficial, just clean it up with warm soapy water and put a band aid or a steri-strip. For a bump, put on some ice to stop the swelling.
Ice and keep clean. What a common injury for a toddler! Clean the cut or scrape with soap and water. If not bleeding too much, or gaping, stitches are probably not needed, but if the cut is large, see your pediatrician. Put ice on the injury to minimize swelling and bruising.