Do not bother with the 'gunge' just take the tyre to a repair place, the gunk will almost certainly not work if there is a screw in the sidewall, and it is only an emergency repair to get you to tyre depot anyway. You will need a new tyre. Once you have that sorted look on eBay for a spare wheel with tyre and put that in your spare wheel bay. I just sold a spare wheel with a new tyre for £15 on ebay, they often go for that sort of price. It does not have to be an alloy wheel if the car has alloys, just a plain steel wheel will do and be a lot better than a tube of goo.