If you have a flat tire caused by a puncture, if you don’t have a spare tire, but have a tire pump, usually you’ll be okay if you use some sort of tire sealant, like Slime. I’d never used it myself until the summer camp work truck had a leaking tire, so I pumped a bottle in and it sealed it up nicely.
As a mechanic I’m not a fan of the various tire sealing products, because they’re just a mess when it comes to taking off the old tire later on. When removing the air from the tire I may get sprayed by green or purple liquid from inside the tire, and when I’ve taken the old tire off the wheel I have to be careful not to splash it all over the place.
If you do get some tire sealant, and you have tire pressure monitoring sensors, make sure you get a kind that’s safe for those, because some can destroy the sensors and you’re now out a couple hundred bucks.