A suggestion to be 'careful' about following, but does work for me.
Your body makes endorphins, which are chemicals that affect your perception of pain. There's quite a few things in life that influence your endorphin levels.
When I need my overall pain tolerance to increase, I try to ensure that my life is overall not too stressful, I try to get a few massages, extra sleep, extra fun and comfortableness.
When that's not enough or not possible, I turn to seriously large amounts of certain spices - like a half a teaspoon to a full teaspoon a day of these (liberally mixed with food, don't attempt to take these as straight powder! - the more you dilute these spices the less 'spicy' they're going to be in your mouth):
White pepper (it's very similar to black pepper, comes from the same plant, and you could substitute black pepper, but I prefer white pepper's taste and 'burn', which is a big part of triggering endorphin production)
Ginger (either fresh or powdered, fresh is probably more effective but it's a pain to work with - powdered is MUCH easier to mix into food, and feels less spicy on the mouth)
Cinnamon (for me, and maybe no one else in the world, dunno, I google with great skill, but I can't find any reports of this except my own experiences - cinnamon in moderately large doses is a mood lifter for me, it doesn't make me euphoric, but it's quite effective in raising my bad moods, and it seems to slightly make me feel less pain too - but pain tends to make me somewhat bad-moody, so cinnamon's part of my anti-pain spices)
Though this is pretty effective for me (about as affective for moderate pain as taking 2 Ibuprofen every 4 hours), it's possible that your body will respond differently. Hope it helps if you decide to try it.