The stars or the bright dots in the eyes can be caused by several reason. Such as hunge, fatigue, and stimulation. In your case, when you sneeze, you get Cerebrovascular contraction, and this will lead to a transient inadequacy of hematic offering to the head. It can be a called sub-health, so I sugget you keeping exercising.
Sneezing is a defensive reaction caused by stimulating nasal mucosa. Trigeminal nerve of nasal mucosa commands the pulmonary respiratory muscles to exhale air violently so as to expel foreign bodies. Such action is so violent that it can cause temporary cerebral ischemia, which manifests stars or some bright dots in eyes.