Why does big toe hurt to walk on but does not hurt to touch?

Hallux Limitus. It sounds like you might be suffering from a condiiton called functional hallux limitus. Functional hallux limitus is characterized by a lack of motion of the first metatarsophalangeal (mtp) joint during gait only. The first MTP joint will demonstrate normal motion during an open kinetic chain examination. If you are experiencing pain see a podiatric foot and ankle surgeon. www.eastpennfoot.com.
Several reasons. It may be that when you walk you are putting the toe in a different position or putting more pressure on it than when you just touch it.