There are a lot of nerves just below the surface of the skin which will have been disturbed and sometimes they can take a surprisingly long time to heal. If you ever recall cutting your finger quite badly, perhaps you can recall it being sore for a long time after the original cut has healed. I don't think it's always possible to state a recovery time as there are lots of pressure points around the body through which nerves run and sometimes for years afterwards a particular spot that has received a trauma can continue to be sensitive.