So, chummels: email the race promoter or call him/her, the name and contact info is on the race flyer. Ask if you got a result, first. Second, tell him about the incident, see if you can get the email address of the chief ref for the race. Tell your story, politely, if you know the rider's number. Word does get around, and, I've witnessed officials give quiet talks to offending riders, and sometimes to their clubs or sponsors. Heal up and race again, smarter next time.