You have to be very careful with red cedar. It is very prone to splitting along grain lines if you wedge anything into it. If the foot went in tight you may need to pull it out and shave it down to a comfort fit.
To repair the damage you can try pulling the cracks back together and if you can they may stay closed with glue; you can fill the crack with colored filler; saw thru the crack the length of the board and glue it back together; or you can drill a long dowel in from the side for reinforcement and that might help keep the crack closed up with glue. If you have some tapered plug cutters like the ones that Lee Valley sells you can cover the dowel almost invisibly.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.