Yep, done it before too - nobody wants to touch a run-flat tire unless you REALLY insist and sign a waiver. Make sure the screw is straight and in the middle of the tread, if it's not, you might need to replace the tire. Also, do NOT let it run out of air/pressure, if it's a slow leak keep some pressure in it. If you drive with a completely deflated tire, you'll end up damaging the sidewalls - if you absolutely need to drive it, you can do so (they're runflats after all) but no more than 80 km/h IIRC.
Do you have OEM Pirellis? If so, they have a comprehensive road hazard warranty which might mitigate the cost of a tire replacement (prorata calculation).
More info here:
http://www.pirelli.com/mediaObject/p...atWarranty.pdf