i had my tongue pierced about two or three months ago and mine got that same looking bump on the side. I didnt play with it or stick it out of my mouth for awhile & kept it superr superr clean! (after every meal, snack, or drink of anything besides water) & it went away :)
also, i rinsed my mouth out aall those times by putting 1 tsp of sea salt in a 20 oz bottle of water and keeping that with me to rinse every time. so its not a thing to worry about unless it gets really gross looking or doesn't heal .
All it is is the equivalent of a scab on your tongue. It will go away when your tongue is fully healed as long as you take good care of it. It'll be worse if you pulled or ripped your tongue any accidentally, which I know happens a lot, often b/c people don't swap out the standard long piercing bar to a shorter one quickly enough. Once the initial swelling goes down, SWAP THAT BAR!
DO NOT use alcohol mouth washes on your tongue. Use one of the newer alcohol-free varieties (I use Crest Alcohol Free and it works wonders).
Your tongue will turn white because you're disturbing the natural bacteria balance in your mouth, but it doesn't mean it's infected. Just be sure to keep everything clean. If it starts turning brown or green, it means you've killed off the bacteria that would keep fungus from growing on your tongue, and fungus has started to sprout because you aren't keeping your mouth clean enough.