I rode bike for 23 miles yesterday and now my eyes are scratchy. What might be the cause and what can I do about it?

Sun, dry or allergy. First congrats on such an endeavor! Several causes of 'scratchy eyes' are possible: sun exposure may have caused slight 'corneal burn' or dry eyes from wind exposure. Allergy conditions may also cause the symptom. Over-the-counter (otc) claritin, (loratadine) allegra, or zyrtec may help. If persistent please see your doctor or ophthomologist.
Dry eye. Your eyes are dry due to wind blowing in your eye during the bike ride. Try using some artificial tears.