I have been having really bad pain in my ankle. it's not bruised or swollen, but it hurts to walk on it. what could it be?

Suspicious: Suspicious for an arthritis or an occult injury. Should consider seeing a doc if this does not clear up in a few days. There are many cause of arthritis ( gout, gonorrhea, lyme disease, post viral, etc) - it is not just for old people.

Injury: Any history of injury? If not need MRI or x rays to check bone. If pain is sharp you may have nerve entrapment.