Hi dear, did u eat anything outside recently? Were u sleeping on your left side for a long time putting pressure? Running nose, fever n nausea point towards an infection.
Next Steps
Is your oral hygiene ok? Do u have any caries or gum infection for which u aren't treated yet? Hope u didn't consume anything very cold or directly from the fridge.
Health Tips
Let me know the answers to all of these n any additional symptoms like throat ache, cough or chest pain. Please do consult here for further assistance.