Engine oil level can be checked either hot or cold and there's no need to wait for the engine to completely cool down before you check your oil level.
When checking the oil wait around 5 minutes before you check the oil as waiting the 5 minutes before checking the oil level allows the engine oil to flow back into the oil pan.
If you check the oil too soon you will get a lower engine oil level reading because some of the oil would be at the top of the engine.
So wait at least 5 minutes to check the oil after you shut the engine off but there's no need to wait until the oil is cold.
When on a road trip I will pump the gas and then after I pump the gas the engine oil has had enough time to flow back to the oil pan but the engine is still hot when checking it and that's okay.
If you're a little under the full mark it's okay but if you have some oil you should top the engine oil off to make sure you have enough engine oil in the engine.