Why would it be that my jaw sore is and locked after braces and rubber bands?

TMJoint issues: It's important to discuss this issue with your orthodontist. Long term, this can be problematic. If your orthodontist can't adequately address your questions and concerns, find a well respected dentist with extensive training and experience treating patients with tmd for a consultation.

You may have a displaced disc. Stop wearing your elastics and immediately call your Orthodontist. Displacement may have already been present changes in relationships do occur during treatment.