Might be more than a sprain. I had a FOOP incident (fall onto outstretched palm, a common enough cause of injury to get it's own acronym) and an x-ray turned up nothing, so it was assumed to be a strain until it was still hurting under certain loads a month later and they sent me for a cat scan - tiny fracture of one of the wrist bones that was hidden on the 2d scans.

I know it's not an option in most of the world but you should always get sprains checked out if you can - there can easily be a small break that causes problems down the road.