You can check your engine oil when it's hot after driving but you will get a more accurate reading of the oil level if you wait at least 30 minutes after shutting your engine off before checking the oil.
Waiting at least 30 minutes before checking your engine oil will allow the oil to settle back down into your engines oil pan after being pumped through your engine.
Checking oil when the engine is hot is not as accurate since there's not enough time for the oil to get back to the oil pan.