Remember that the oil light has nothing to do with oil level, its oil pressure. Most cars will work fine with under minimum if you just drive on flat roads with no turn.
The fact that there's oil in the pan does NOT mean that the engine is lubricated.
The fact that the oil light comes on means one of two things, either you have a eletrical issue, or you have a problem with oil pressure. Always assume worst case scenario witch is bad oil pressure, at this point you should not drive the car at all before you can confirm that you in fact have some oil pressure.
For checking your problem: start with checking timing belt, and the vaacum pump.
And by all means, check for eletrical issues, issues with the oil pressure warning system is far more common than actual oil pressure problems:-)
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