Here is a list of some common injuries and the average duration that you should feel pain from that injury. If your pain lasts any longer, you should seek medical attention.

Sprain
Ankle - 1 week
Knee - 3 days
Wrist - 3 days
Finger - 1 day

Low back strain
Minor - 1-2 days
Major - 3-5 days

Burn
Small - 3-6 days
Large - several weeks

Splinter - immediate relief upon removal

Skin cut - 24 hours

Headache - Hours to days

Chest pain
Surface soreness - 1-4 days
Heart cramp - 1-10 minutes
Hear attack - Hours to days

Stomach pain
Indigestion - Minutes to an hour

Abdominal pain
From overeating or constipation - 1-3 hours

Shouldn't you probably seek medical attention after a heart attack or heart cramp anyways?!?

I was suffering from arthritis in my low back, tail bone pain and my left foot was turned inward and I had been walking that way for 12 years. My Orthopaedic doctor had only given me insoles for my shoes. Millstone was amazing because my left foot has been straight since my first treatment and my back pain has gotten better every day. i also no longer have any pain in my tail bone. It's a GREAT feeling to be able to walk normally without pain or added pressure on my ankle.