If the intake screen on your oil pump is intact I doubt the piece of dipstick would get picked-up by the pump or elsewhere; if you really overfilled the sump you might aerate the oil enough to get if off the bottom (but I doubt it). But, you'll never feel comfortable knowing it's in there; esp. on longer trips. I'd say you can drive some but drop the pan when you get a chance; it's not a terribly tough job, unless the pan was sealed with some strong adhesive sealant like Right Stuff (there's a thread on this on this Forum somewhere). Not a bad idea if you haven't had the pan off in a long time to check for sludge, (other) metal bits, etc.