Check engine light came on Need Help!

ok here is the deal… i am driving around today car seems to be running fine than i go get gas than drive around for a bit more on my way back to my house i realize my check engine light is on i pull over check the engine everything seems fine check the spark plugs nothing on them… i have no idea whats going on. the only thing we did was killabeez cleaned my engine like he did his but he didnt spray the valve cover with as much water… so i dont know if thats the reason… this sux i gotta drive to boston tomm and i dont wanna get stuck!