Check Engine Light

Hi! Everybody! I need some help or I guess I should say, that I have a question about my 93 2.3 Vert mustang! I have been driving the car for weeks now, and two days ago i was driving it and noticed the check engine light was on.....So i parked and left it alone for a couple days, and then I realized that the hood wasnt fully secured down when I had been driving it those days...pretty dumb not to notice that, I know....but I've driven it all day today and the light never came on....so my question is...might that have been the problem in the first place? Is there a sensor for that on the car? Or is something totally unrelated? I dont know why it would come on for a day and after a full days driving today...everything has been cool?

See my first thought was to take it to autozone or oreillys to check it right as soon as it came on, and i was kinda taken aback....neither autozone or oreillys carries equipment to shoo codes anymore for car older than '96...Which blows because I dont have any friends who have a meter or and I dont want to spend money to figure it out...i dumped too much in it already and im selling it.