Is the blade actual wood or pressed wood fibres? Real wooden blades may be glued and clamped together until dry. The other types may not be able to be repaired due to the composition of the blade. It maybe glued together, but may not stay glued together once the fan is turned back on.
Buy new one
May be check out a Value village or a second hand store to see if you could purchase one blade like yours!
You seldom can repair a blade, because
A. the push momentum will cause that same blade to break over and over again.
B. Any 'tough enough to survive the momentum' solution will imbalance the fan and that can create problems in the ceiling.
So, You need to instead
1. order replacement blade(s) from the original manufacturer to remove the old blade(s) and install the new one(s)
or
2. just buy a new fan
Usually resolve #2 is less expensive when you are dealing with 'Newness mismatchings of the Old blades with the new'.
Is the blade actual wood or pressed wood fibres? Real wooden blades may be glued and clamped together until dry. The other types may not be able to be repaired due to the composition of the blade. It maybe glued together, but may not stay glued together once the fan is turned back on.
Buy a new once at home depot, or go to Habitat for Humanity and pick up a used one.