The reason the branch that broke off smells like grass is because the buds on that branch did'nt reach full maturity and the trichomes were probably something like a 50/50 clear to cloudy ratio. When buds are harvested before they are truely ripe and mature, which is based on a few factors BESIDES what the trichs look like, they will often have that grassy smell. If you continue to cure it properly though atleast most of that will dissipate and smell more like what your used to but the grassy smell will not completely go away. Let the rest of your plant fully ripen and you will notice the difference between your broken branch and the rest after you've cured.