I recently started to have a heated/burning sensation under my big toe. no associated pain noted. what could cause this?

Nerve entrapment: Burning pain associated in the foot is mostly from nerve entrapment syndrome. This is caused by over-pronation of the foot and thus causes instability across the toes. This commonly may push on the plantar nerves that run between the toes, causing a burning sensation. If it feels better to rub them when it happens, most likely a nerve issue.

Few things: Could cause this. First, i would examine the skin to see if there is any sign of cracked skin, blistering or scaling as a fissure or athletes foot may be present. If not, i would question you with regards to low back pain or if you are possibly diabetic. I would also evaluate you for compression neuropathy of the deep peroneal nerve or tarsal tunnel syndrome.

Nerve pain: You could also have a tear in the tendon. Go see your podiatrist.