What is the reason for burning rash with blusters spreading quickly around lower back and near groin?

MAYBE SHINGLES. Get seen=you may have shingles (zoster) rash! . It first presents as severe burning pain then quickly turns into a blistery rash (generally on only 1 side of the body). Early treatment may help prevent post-herpetic neuralgia --a painful complication. Hope you are better soon!