SolasLunas: Shortest answer:
your tongue always had those bumps, but they are usually very small. If something is to hot/sweet/salty than it’s prepared for, it will swell. This brings in white blood cells faster than usual since your body isn’t certain if it’s an infection or not, and it also circulates the blood more so the temperature is regulated and the cells have the resources to repair any damage.
More detailed answer:
Your tongue is always made up of these little bumps called “Lingual papillae” (unless you have a certain health condition that causes the tongue to have a smooth and irritated area.)
When they are burned or come in contact with something that is extremely sweet or salty beyond what it can tolerate, the area gets irritated by the extreme exposure and will swell, making them more visible than usual as a side effect
The area swells as a side effect of increased blood flow which helps regulate temperature, deliver nutrients to repair any damaged cells, and deliver an increased amount of white blood cells in case there is an infection. The body tends to respond to negative stimulus by sending in all the available methods of treatment so even if your tongue is just burnt you will get the automatic responses intended for temperature, physical trauma, and infection all at once just to be safe.