What to do if i have achilles/ankle hurts very badly?

Get examined: Pain in the ankle and back of the heel towards the back of the leg is where achilles tendonitis occurs, but are you sure that's what you are dealing with? Get examined properly. Xrays can infer position of soft tissue but mainly highlight bone. To examine the achilles, an MRI would be warranted to check for damage - even a longitudinal tear which can be very subtle but result in lingering pain.