As a general rule, cannabis strains with high amounts of both THC and CBD tend to make the best pain medicines, ACDC is a good one if you can find it.
High-THC strains also offer pain relieving benefits, and many people find that heavy Indicas work well for Chronic Pain & the Insomnia that comes with it.
I'd have to same some of my favorite strains for pain relief are, Cherry Pie, Thin Mint Cookies and Lavender Goo.
Physical pain has a more of a chance of subsiding when the mind is relaxed too. These strains have brought me a lot of relief.