Following a root canal is it normal to have a little bubble by the tooth and hot/cold w tenderness, what to do?

No: No. Sounds like an abscess. May represent failed root canal and the need for extraction.

Another tooth: A root canal tooth does not have a nerve in it so you cannot have a hot/cold tenderness on that tooth. However it could be a tooth next to the root canal tooth. This needs to be evaluated by the dentist.

Go back to your DDS: Questions: when was the root canal finished. The first 24 hours are typically the worst. Hot ; cold sensitivity would be unusual since the tooth is dead. I would make sure that your temporary is out of occlusion. Where is the bubble? If your root canal was yesterday and the bubble is on the gum line perhaps the rubber dam clamp could have done it. If the bubble is at the root apex it is infection.

Bubble by the tooth: The symptoms you describe indicate an infection. Either the tooth that had the root canal treatment has not yet healed, has re-infected, has a root fracture, or it is another tooth. See your dentist for an examination to evaluate the root canal and the neighboring teeth.