What would cause a broken blood vesil in my eye ?

Tiny pressure bump: Commonly seen from sneezing, coughing, bearing down, heavy lifting, and the like. Unless you are are on a blood thinner, it is just a "thing" and no evaluation or treatment is recommended. It is a small bruise, just under a clear layer and not subdued by skin, so can look quite nasty. If on blood thinner or involves 1/2 or more of the sclera (white part), call your eye Dr or get checked in ER.

Several causes: trauma, rubbing, high blood pressure, thin blood, medications, clotting disorders, Valsalva, etc.