The accident happened along La Vrangue last Friday tea time, as the boy was indicating to turn right on to Mont Arrive.
Guernsey Police say the car hit his right hand as it overtook. The boy’s hand was fractured and he now needs an operation to fix it.
It happened between 17:45 and 18:15 on Friday 27 September and any witnesses are asked to contact PC 175 Clarke with information, on 725111 or Crimestoppers anonymously on 0800 555 111.
The boy was riding an orange push bike, but no details have been given about the car.