He took a tempra for his fever fri-sun.he was fine by monday but there was a burn like came out of nowhere on his abdomen and its getting larger.

See your Dr: Several diseases can present with blister like lesions/burns with fever. Skin infections, shingles etc. I would take your nephew to see a Dr as soon as possible so that he can get the right treatment - the sooner the better!

See a doctor: Then he needs to see a doctor and have the issue evaluated. He needs to be examined and lab tests need to be done.