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?!?