Poor Posture – Sitting at a desk all day, looking down at your phone, or sleeping in a bad position can strain the muscles in your neck and jaw.
TMJ Disorder (Temporomandibular Joint Dysfunction) – If your jaw joint is tight or misaligned, it can cause pain near your ear and radiate down your neck.
Grinding Teeth or Clenching Jaw – This puts stress on the muscles around your jaw and neck, leading to pain.

Nerve Issues

Pinched Nerve (Cervical Radiculopathy) – A compressed nerve in your neck can cause sharp or aching pain that starts under the ear and travels down the neck and even into the shoulder.
Occipital Neuralgia – This happens when the occipital nerves at the base of your skull become irritated or inflamed, causing pain that radiates down your neck.

Ear Infections & Sinus Issues

Ear Infections – A middle or inner ear infection can cause pain that extends to the neck. If you also have ear fullness, hearing issues, or drainage, an infection could be the cause.
Sinus Infections (Sinusitis) – Pressure buildup from sinus congestion can cause pain behind or under the ear and into the neck.

Lymph Node Swelling (Infection or Inflammation)

Swollen Lymph Nodes – If you have a cold, flu, strep throat, or another infection, the lymph nodes under your ear and down your neck can swell and become tender.
Tonsillitis or Throat Infections – Infections in the throat can cause radiating pain under the ear and down the neck.

Dental Issues

Tooth Infections or Abscesses – An infected tooth can cause pain that spreads toward the ear and neck.
Wisdom Teeth Problems – If your wisdom teeth are impacted or infected, they can cause discomfort in the jaw, ear, and neck.

More Serious Causes (Less Common but Possible)

Mastoiditis – A rare but serious infection in the mastoid bone behind the ear, causing pain, swelling, and possibly fever.
Temporalis Arteritis – Inflammation of blood vessels near the temples, which can cause pain around the ear and down the neck.
Tumors or Growths – Though rare, certain tumors near the throat, lymph nodes, or jaw could cause persistent pain in this area.

How to Treat It

For Muscle Tension

Try heat therapy, stretching, and posture correction.

For Nerve Issues

Gentle neck stretches, massage, or anti-inflammatory meds may help.

For Infections

If you have ear pain, fever, or swollen lymph nodes, you might need antibiotics.

For Dental Problems

If you suspect a tooth infection, see a dentist as soon as possible.

When You Might Need Real Medical Attention

If the pain is severe, persistent, or getting worse
If you have fever, dizziness, hearing loss, or swelling
If you notice numbness, tingling, or difficulty swallowing

If you’re not sure what’s causing the pain, I’d start by checking if it’s muscle-related (try stretching) or infection-related (check for fever or swollen lymph nodes). Let me know if you need help figuring out how to relieve it.