Don't worry. From your symptoms and doctors words, it sounds like a localised traumatic sub conjunctival haemorrhage, which is a blood leak above the visible white part(sclera) of the eye called Conjunctiva.
It usually takes 10-15 days time to resolve completely.
Wait for a day and if the redness
is spreading with watering and irritation , have a second opinion
, as it could be an infectious conjunctivitis
or an allergic one too.
Meantime avoid rubbing the eyes as it aggravates the symptoms.
Hope this helps.