The full width half max of a signal in NMR is related to the relaxation time of the signal (specifically the T2, or spin-spin, relaxation). This can give you information if your nuclei undergoes any dynamic processes (e.g. tumbling in solution, chemical exchange (like hydrogen bonding), rotation, conformational dynamics, etc.). I'm not sure what specific information from T2 relaxation is important for boron NMR, however.