You can likely save your tree.  Don't try to seal the crack - it  should naturally heal.  It will likely form wood around the damaged area, which will help with sealing.  Your tree will be more vulnerable because of the crack, so monitor it for infection.  You could also wrap the trunk in late fall, removing it in the spring, to help prevent further cracking.  For more information, see https://homegarden.cahnr.uconn.edu/factsheets/frost-cracks-and-sunscald-on-trees/