I just imagine green healing energy going to the spot of pain, ground myself, or put a shield on it that takes the energy of whatever ails me and replaces it with green healing energy
Of course, "healing energy" can be a different color to everyone. It may be clear.
I know how to stop pain.
1) Meditate. A good meditation is imagining that you are at the beach and you imagine the sounds of the beach. While imagining that count backwards from 100.
2) Your mind should get really clear that you can imagine that you do not have any pain.
3) When you are out of the trance your leg won't hurt anymore.(If done correctly)
I prefer these methods over meushiman's methods because they work quicker and more effectively.
Or you could do it the really simple way like Meushiman that probably would have been good to know.
Simpler isn't always better. Well, in this instance, it isn't.