Since you are a Canadian citizen, they cannot deny you entry to Canada. However, Canada will see the warrant and hold you pending the request for extradition to California. Whether or not you are extradited depends on 1) where the incident occurred 2) the exact charge 3) the dollar amount on the warrant and 4) the age of the warrant. I would advise you to speak with a criminal defense attorney.
Seth Weinstein, Esq.
Los Angeles Criminal Defense Attorney
This reply should NOT be considered a legal opinion of your case / inquiry. At this time I do not have sufficient factual/legal documentation to give a complete answer to your question and there may be more to the issues you raised then I have set out in my brief reply.
Yes, I would be worried. Unfortunately no attorney in the US is going to be able to give you very good advice. You need to contact a Canadian immigration attorney, not a California criminal defense attorney.
I suggest contacting a Canadian immigration or defense attorney for help with this. It might be wise to hire a locally experienced defense attorney in the US upon your return to Canada to try to allow you complete your probation in Canada and get the warrant recalled. Best of luck.