Many things. Diverticulitis leaps to mind, although you are young for it. Also hernia, trauma, associated skin infection, tick-bite or other insect, skin rash from chemicals and a myriad other possible causes! See your doctor to figure it out!
Unknown. There are a number of causes for inflammation of the colon. Common causes include diverticulitis and bacterial or viral infections. A careful history and physical exam, along with reviewing any diagnostic studies needs to be done. You certainly should seek out a trusted physician to get your answer.
(L) abdomen inflamed. Do you eat many nuts or a lot of popcorn or things with tiny seeds? Do you have a history of diverticulosis or rectal bleeding when you eat the things mentioned above? Any change in bms? Any history of trauma to left abdomen? See fp for evaluation, imaging &/or testing if necessary, treatment.