Or if you are not comfortable doing that you can send it to a reputable call maker and have him help. Kelly Beltz offers those services and does a fine job. I have personally had John Koepp from Addiction fix a call barrel (from another maker-RNT) for me once free of charge and he did an excellent job.
If you haven't done anything yet, try some isocyanate wood glue (aka Gorilla Super Glue). Use a small pick or something similar to open the crack just a bit. Squirt the glue in and squeeze. Should be dry in about 30 seconds and should hold forever with no noticeable effect to the call.
I feel slightly sorry for a man who has never patterned his gun, who has no idea how far his chosen load will retain killing penetration. But I'm extremely sorry for the ducks he shoots at beyond the killing range of his gun and load - Bob Brister