When walk for a short time my left ankle starts to hurt for no reason, it feels very painful when i walk. what is going on with my ankle?

Well if there is : Pain there is a reason, it is just not known yet. Sounds, like you need to see a specialist who will examine the foot, place it thru range of motion and palpate for a region of pain. An MRI may be warranted to help come to a working diagnosis.

There is a reason: Pain is not normal so there is a reason. I suggest rest, ice, elevation and compression and see your local podiatrist for x-rays and possible MRI to find the cause then it can be treated.