Ticking... possibly injectors.

[sbird1]

So I was driving up to school yesterday, and about 10 miles out, my motor started to tick. I thought I may have been low on oil so I stopped. I was less than a quart low, so I filled it back up, hoping that would solve the problem... it didn't. I'm about to try and listen to the injectors via a screw driver but my question is really this. Why do the injectors tick? And more importantly, is it Ok to drive? I am limited in my tools and things here and I will fix the problem when able.

EDIT: I'm sorry I made this thread. I should just search. A mod can feel free to delete this if they want...