I give you the Ultimate Painkiller: 2.5ml of Alcohol

Pour 10ml of alcohol into a small container, like a tea cup or perfume bottle with 100ml capacity.
Fill the container with any drinkable liquid like milk or soda, water doesn't really work because you can't manually drink water without being thirsty.
Now, whenever you feel pain, just take a 1/4 sip into the alcohol mix, because you are drinking alcohol the pain level would immediately drop, but also because you drink so little alcohol (only 2.5ml) the Drunk moodle would last like 3~4 seconds.
You can sip it before bed for instant sleep with severe pain, you can sip it at battle when muscle strain was giving you agony pain, you wouldn't get that much of drawback at the field since the drunk moodle last so short.