The other girls are right. If they were huge and red before, he probably had a mild tonsilitis, on top of what are naturally large tonsils.

Unless he has so many infections that it is affecting his growth or development, or he develops sleep apnoea, then it is safest to leave them be. A generation ago we used to take out a lot of tonsils, but the operation is not without it's risks, bleeding being the main one, and I have not long ago looked after a child that ended up in hospital for a week after a post-tonsillectomy bleed, and they nearly bled to death. So the practice now is to leave them alone unless there are clear reasons to take them out.