I have never heard of a head injury causing red, sore eyes. My suggestion is allergies/hayfever. This is about the time for grasses to be going to seed. Rye grass is a common hat fever allergen.

There are other airborne irritants that can also cause red, sore eyes. Here in Idaho, we have smoke from wildfires.

A simple test is to take a hayfever med. If it resolves the symptom, the diagnosis is made. Ask the pharmacist which med works for eyes. You can also buy eye drops for allergy eyes. They work very quickly. I need them during the rye grass season at my cabin.

My best to you.