graph homomorphism density inequality

Question

I'm just reading the book "Large networks an Graph limits" by Lásló Lovász and I am trying to solve an exercise in the book. If $F$ and $G$ are two simple graphs, then their homorphism density is defined as $t(F,G)= \frac{hom(F,G)}{v(G)^{v(F)}}$ and and similar the injective homorphism density is defined as $t_{inj}(F,G)= \frac{inj(F,G)}{(v(G))_{v(F)}}$ where $inj(F,G)$ is just the number of injective Homorphism from $F$ to $G$ and $hom(F,G)$ is the number of homorphisms from $F$ to $G$. I want to show that $t_{inj}(F,G)\leq t(F,G) + \frac{1}{v(G)} $$v(F)\choose 2$. Would appreciate your help :)