Foot numbness due to diabetes. What should I do?

Seek treatment. If you haven't or currently not under the care of a foot and ankle specialist, seek treatment. You should be properly evaluated and appropriately treated. Numbness in a diabetic patient could be the development of peripheral neuropathy which can lead to further complications, seek treatment with a specialist.
Be evaluated. Be evaluated by a foot specialist to ensure you do not have any other accompanying factors. The doctor will let you know how frequently you need to follow up based on your clinical findings.
Have it evaluated. Topical capsaicin may be helpful for some, while others may benefit with oral medication such as Pregabalin (lyrica), Amitriptyline (elavil), duloxetine (cymbalta), Gabapentin (neurontin), Carbamazepine (tegretol), or valproate (depakote) to reduce the painful symptoms in the feet due to neuropathy. Watch you sugar intake, and have your vitamin b levels checked and supplemented as necessary.