I just suddenly had like a glassy vision in my left eye that lasted about 10 minutes and thereafter got a headache. also felt slightly nauseous. is this anything to be concerned about?

If your history includes headaches of the migraine type, the symptoms may be related. If not, a mild TIA (transient ischemic attack) may also cause visual symptoms and headaches. Get a neurology referral to ascertain the cause and the potential severity of your symptoms.

You could be experiencing periods of increased pressure in the eye with the glassy vision due to corneal edema from the high eye pressure. Symptoms such as this can be seen in Fuch's iridocyclitis. You need to see an ophthalmologist.

I agree with Dr. Yarichs’s answer and you may want to consider as well a migraine. Yes, go to an Ophthalmologist, but if it happens again , please go to the ER. They will be able to diagnose you, likely get rid of your headache and set your appointment with the right specialist. Don’t let it pass.