hey,
It possible that xrays miss very small fractures. In that case brace not likely to do much. in that case i think you probably just need to rest for a couple of weeks.

And because u describe the pain as being the worst behind the ankle near the achielies again the brace is unlikely to do much. In my opion, brace is more likely to help if you have lateral or medial pain, rather than posterior pain.

Best off to see an experienced physiotherapist first to get a full assessment. good luck.