how to unlock 98 chevy s10 ignition?

I have a 98 s10 and the other day my boyfriend not paying attention tried to start it with the key to my saturn. when he relized it and tried to start with right key it was usless the ignition and steering wheel was locked. the key will go all the way in and the bell for the door dings but thats it. we are low on cash and can't take it to a locksmith but when it comes to cars were stupid!!! so if anyone can spare time for step by step help it would be greatly appriciated. Thanx bunches!!