Sharp pain from my big toe shooting up to my back happens occasionally, what can it be?

Nerve impingement. Something is irritating the nerve travelling to this area. Often it is a bunion bump that is rubbing against the shoe. There is a small nerve that is right under the skin and goes on into the big toe. See a podiatrist for an exam, diagnosis and care.
Sciatica. Could be a pinched nerve from the lower back causing this discomfort. Recommend x-ray to rule out any pathology around the great toe.
Entrapment . Likely a nerve entrapment. Possibly from low back. Nerve conduction study would be helpful.