Minecraft wiki entry for Nether_survival, associated text: Always bring along a flint and steel because even if you don't intend to build a new nether portal, a ghast fireball can easily break a portal block inside the portal frame, leaving you stranded until it is relit with fire from a flint and steel, a fire charge, burning blocks adjacent to the portal frame, or even another ghast fireball. If you forgot to bring a flint and steel, all hope is not lost -- you can bargain with Piglins for iron (or find one in a chest), or you can make a fire charge from Nether materials (Wither Skeleton for coal, a Ghast for gunpowder, and kill a blaze for blaze powder).