If the oil level is at such a level which may cause some serious damage, you will probably notice some white smoke coming from the exhaust, also, if your car has an oil pressure and/or level gauge, you will see it running very high even when warmed up. I would use an extractor pump and suck some out through the dip stick tube. The worse case scenario of an oil overfill will result in compression leaks, blown gaskets, and over-compression of the combustion chamber. Essentially, you may have an engine rebuild. Just make sure you are wiping the dip-stick properly before checking, sometimes the dip-stick picks up oil from the tube its-self if some was deposited there during filling or checking.