In general, grinding the baby teeth is not a problem. It is often a sign of teething, very likely for a 12 month old. When he starts losing his baby teeth, the grinding should stop (if it even lasts that long). If he is grinding his adult teeth, then that is a different story, and a dentist should be consulted to look for damage. He might suggest that a tooth guard be worn while sleeping.
“My 12-month-old grinds his teeth while awake and sleeping what can I do to stop him and will it hurt his teeth?”