Sounds like a valve cover gasket leaking, that's an easy, quick and cheap fix. Try tightening the valve cover down first to see if it stops. Don't over tighten the bolts! If that doesn't correct the problem you'll have to replace the gasket. This is still a fairly simple procedure. If you don't fix it, it's not going to hurt anything, but it will get worse over time and leak more. You'll use more oil, but eventually the oil will work it's way down to the exhaust manifold and start burning, causing an annoying smoke to billow out of the engine compartment.