Ask him to take some over the counter pain reliever and consult a doctor
for examination and antibiotics prescription. If there are recurrent
boils, then please get his blood sugar levels estimated. Also since he has had many courses of antibiotics, so he needs to get a culture sensitivity of the pus from the boisl done so that specific topical as well as oral antibiotics can be prescribed.
I hope that helps. Take care and please do keep me posted in case you have any additional doubts.