ant bite or insect bite can cause allergy
rednaess and swelling and itching some times burning also. I was yesterday it should settle down by itself,or if he has itching a tab of antihistaminic like levocetrazine may be taken.locally some soothing lotion may be applied. Some time allergy is serious like anaphylaxis
or angioneurotic oedema ,if you suspect any thing serious then visit Emergency Room. Hope every thing will be fine all the best.