Sudden sharp foot (top) pain when i stepped down. hurts to flex foot upward, not down. not tender. trouble moving toes. hurts to wal causes?

Tendinitis: Tight shoes or an old injury can irritate and scar the tendon coverings & the extensor tendons inside. Foot soaks in plain warm water (Epsom Salts are worthless) may help. Padding in your footwear & avoiding straps over the instep can help. If you can localize the tenderness & you love the offending shoe get the shoemaker to soften that area with his swan neck tool. Neatsfoot oil softens leather.

Tendon.: It sounds like you may have damaged a tendon or two on the top of your foot. It is probably best not to test it by extreme movement. To remove all doubt, have your foot examined by a specialist.