For the past 2 years i've been having pain in the back of my lower left leg. i don't work out, can this be some type of cancer?

Leg pain: You have a problem -- leg pain. The problem is chronic and apparently without a diagnosis. The differential diagnosis (ddx) includes many things. Cancer is on that ddx list, but isn't near the top. See a doctor to evaluate for musculosketal issues such as bursitis, neuropathy (sciatica), arthritis, muscle strains, etc. This may include imaging or other specific tests.

Still around: It is unlikely to be a cancer--after all, it's two years later and you're still around! it is more likely to be muscle strain or, if lower down on the leg, tendonitis. A cancer of the leg would most likely be a sarcoma, and this would usually show itself as a lump or mass that grows.