New crown; back molar 6 wks ago. ate on that side and now gum around the crown is sore. how long does it take a new crown to settle? how can i relieve the soreness? thank you?

The inflammation may or may not be due to the crown. Are you trapping food? Has the gingiva been inflamed for six weeks? New restorations don't need time to settle in (except for maybe dentures as soft tissue remodels a bit). If soreness continues for more than a day or two see your dentist for a follow up.

Your condition is best that you return to the dentist and have him/her check what is happening. If a regular x-ray did not show anything and all tests are normal, but if your condition continues, the next common step is to take a 3D scan to see if the images of the bone in the area show any sign of disease or conditions. The crown may be a bit too thick/high also. Ask the dentist.