I sprained my ankle in early april. I can walk on it, but it's still very sore. What else might be going on?

Cartilage damage. These type of injuries can also create damage to the cartilage surface of the talus bone, the lower surface of the ankle joint. These are called talar dome fractures or osteochondral fractures. Somitimes these may not be visible on a plain xray and your doctor may order a ct scan or an mri. Depending on the size of the fragment immobilization may not be enough and surgery may be needed.
Divot in cartilage. One thing it could be is what is called a "talar dome lesion" (meaning a divot in the cartilage of the ankle joint). An MRI can evaluate if this or any other problems relating back to your ankle sprain are present.
Not uncommon. It is not uncommon for an ankle sprain especially if severe to hurt for 2 - 3 months. This happened to myself. You should protect it in an ankle brace however, when walking. Stenghtening of your peroneal muscles are a good idea. If you have any doubt that something else is wrong- then see a podiatrist or orthopedist.

Related Questions

Should my ankle sprain swelling have gone by day 5? Was only mild sprain could walk afterward, its just still really swollen and a little sore now.

Time, time, time. Ankle sprain swelling can take as long as a year to resolve. Almost never is it resolved by 5 days. The worst of the swelling typically resolves over 6 weeks. Do not let the presence of swelling cause you to restrict your activities. Instead, let pain be your guide.