Probably not yourself, no, and the fissure will not fuse back together again. (Plant injuries can't heal and mend in the same way ours can.) This might have resulted from a phenomenon called included bark which prevents strong branch attachment and is a common flaw on many cultivated trees with poor branching. A University of Florida Extension tree pruning publication discusses how this occurs.

Don't coat, fill, or seal the wound with anything, but you can consult with a certified arborist about your options for stabilizing the tree, plus to review the overall health of the tree in general.

Miri