Hello all. I got two nails in one of my rear tires on my 2016 Outlander with about 35k miles so its unrepairable and am now driving with the spare.

Can I replace the tire by itself, or do I need to change the other tire on the same axle?

Should I go the Mitsubishi dealer to get the same exact tire? Costco for example only had Michelins. It's quite a distance to drive but I'll do it if I must.

Also -- if I replace one or more tires in a 3rd party place, do I still maintain warranty coverage?