It seems like your son had a cut lacerated wound on the head which was patched up with glue to prevent scar formation.
It seems like it was a minor injury and the fever has developed because of the pain. It is important to rule out other causes of fever on trauma like infection at the site of laceration. Gently observe if there is excessive swelling or pus from the site. It there is a little pus, you can safely wash the site with warm soap water or an antiseptic solution. You can give him 0.4 ml or quarter tea-spoon of Tylenol oral suspension.
IF there is excessive pus draining or increased swelling at the site, I would advise you to take him to GP who might do a better job cleaning the site. He might even open the glued area to give it an antiseptic wash and prevent spread of infection.
I would also advise you to look out for signs of internal brain trauma like continuous vomiting and excessive drowsiness.