In general there is no relation between automorphism groups of subgraphs and the main graph. However, this question is about vertex transitive graphs.
Given vertex transitive $G$ and $H$ such that $|\mathcal{V}(G)|<|\mathcal{V}(H)|$.
If $\mathcal{Aut}(G)\supset\mathcal{Aut}(H)$, is $G\leq H$?
If $G\leq H$, is $\mathcal{Aut}(G)\supset\mathcal{Aut}(H)$?
(I suspect the answer to the second question is no.)
Given vertex transitive $G$ and $H$ such that $|\mathcal{V}(G)|>|\mathcal{V}(H)|$.
If $\mathcal{Aut}(G)\supset\mathcal{Aut}(H)$, is $G\rightarrow H$?
If $G\rightarrow H$, is $\mathcal{Aut}(G)\supset\mathcal{Aut}(H)$?
(Again I suspect the answer to the second question is no.)
$\rightarrow$ implies homomorphism exists in the direction suggested.