Blowing vigorously may have caused mechanical stress
upon the internal structure of the eyes the vitreous and it's attachments to the retina
. Any mechanical stimulus to the retina will cause abnormality of vision. Are you a mope and what is your age like.
Flashes or photopsia is a clear indication that some abnormal stimulation of retina occurred. You may get an indirect ophthalmoscope done to rule out any retinal problem and its timely management.