I had a grade 3 ankle sprain just over a yr ago and still have dull pain and bruising/discoloration, what should I do?

See a doctor. A podiatrist or orthopod should be consulted to see if there is any residual damage caused by the sprains. The discoloration could be staining of the skin from "heme" escaping from the blood vessels during the trauma.
Follow up with DPM. You may have a chronic problem with a concomittant acute process. It is best to see a foot and ankle specialist. Xrays will show most bony pathologies whereas an MRI will expose underlying soft tissue injury as well as bone and cartilage pathology.
May need an MRI. Limit your activity for now and have it re-evaluated.
See an orthopod. True grade 3 injuries continue to cause problems usually for one of two reasons. Either there is an associated injury (talar dome injury, non-healed lateral ankle ligaments, scar tissue in the ankle gutter, etc.) or the more common reason is incomplete rehabilitation of the ankle with decrease proprioception and achilles tendon tightness. Get the diagnosis right and the treatment will follow.