What could be making my gums hurt behind a back tooth that was hurtin me a wk ago after eating.tooth stopped hurtin but gums do now i can hardly eat!

Difficult to : Diagnose, but my thought is you might have some food impaction / particle lodged under the gum. Normal culprits are popcorn, chip fragments ... Best to be seen by a dentist for an x-ray and evaluation to correctly diagnose and treat. Hope this helps.

Wisdom tooth?: If you haven't had your wisdom teeth removed yet, your first sign that you have wisdom teeth may be an infection of the gum behind your back molar. As this new tooth becomes exposed to the bacteria in your mouth, the gum over it can become infected to the point where you may need antibiotics to treat it. See your dentist or oral surgeon before it gets out of hand.

Periodontal abscess: Food or debris lodging into the gum causing localized acute infection. Brush the area thoroughly and schedule with your dentist for xray. Also possible endo abscess from the tooth. Check your occlusion for food impaction due to open interproximal contact between two teeth.