What are symptoms of broken ankle bones compared to just a bad sprain?

Both hearts. The symptoms of both pain and deformity discolored skin, but when you examine the person with broken bones he will have tenderness were the bone broken were is no ligament, of course the x-ray will help. Good luck.
Get an xray. Pain with direct pressure on the bone vs the ligament both will give pain, swellng, difficulty walking get an xray.
Break vs Sprain. It is often difficult to tell if you have a bad sprain or fracture without x-rays and sometimes mri. Push with your fingers directly on the bone, then press on the tissue at the end of the bone? Bone pain may indicate fracture. It would be advisable to see a doctor and at least get x-rays done. Untreated breaks, or ligament damage can cause long term damage.