My jaw locks on one side when i try to eat waht is it?

Locking Jaw: The jaw can "lock" due to a variety of causes. If it locks when you chew food, it's most likely due to a displaced disc in the jaw joint, or tmj. The disc may be partially or completely displaced. Only an MRI can tell for sure. In the mean time, try a soft, non-chewing diet, nsaid's and perhaps a muscle relaxant. If these don't help, see a dentist or oral and maxillofacial surgeon who treats these.