i am worried with my son

I think that's already an infection. Anything that involves fever might suggest infection considering the fact that your son has canker sores. Try to consult a doctor before prescribing medications because without complete assessment, it might put your son's life at risk. It can also waste your money cause what might other people suggest you is not effective. So don't take risks. Hope your child will get well soon.

If you can let your son rinse his mouth with aloe juice frequently then do it. Put some alum on the canker sores. Repeat this twice a day. It helps to relieve the pain and quickens healing. Apply some baking powder on the sores. It could be used either in the powdered form or in the paste form. It will reduce the amount of bacteria in the mouth, Rinse your mouth several times a day by a mouthwash prepared by mixing one tsp. of baking soda in half cup of warm water, Prepare a mouthwash by putting 5 to 6 drops of Grapefruit seed extract in a glass of water. Rinse your mouth with this at least once in a day. It is an excellent disinfectant, Prepare a mouthwash using three parts of water and one part of hydrogen peroxide. Use this mouthwash twice a day, Onion is another excellent home remedy for canker sores. Apply some raw onions to the sores, Rinse your mouth with plum juice. If the sore is too bad then apply the juice on the sore using a cotton ball, Eat fresh papaya fruit or chew fresh papaya leaves. If fresh papaya leaves or papaya fruits are not available then you can also use papaya tablets, Gargle your mouth with a solution made by mixing 1 tsp soda and 1 pinch of salt in a cup of warm water, Apply tea tree oil to the sores, Rinse your mouth three to four times a day with a solution made by mixing 2 tbsp. salt to 6 ounces of warm water, Apply some powdered Goldenseal powder to the sore or rinse your mouth with a mouthwash prepared by mixing ½ tsp Goldenseal powder to ¼ tsp salt and 1 cup of warm water.

My son gets those too. I would follow what others have said here to get rid of them, bit it's important that he uses a good mouth wash or use a warm salt water rinse so he doesn't keep getting them. My boy starting doing this everyday and he doesn't get them anymore.

a teaspoon each of liquid Maalox and Benadryl it works for all types of sores associated with the mouth. My middle one used to and still gets sores if she eats something with too much salt so maybe try to cut back on salty snacks.

aloe vera plant. break off the leaf, burn the tip so that it bubbles, peel off the black, and put the gooey stuff on his lips. It wont hurt him if he eats it but it does tast kinda nasty.