My 3 year old has a lot of bumps all over his body, what can it be? When I put johnsons lotion he says it burns him. Can you help me please

See pediatrician. It could be an allergic reaction in which case it would be red, raised and very itchy. Hydrocortisone works well. It could also be from a viral infection. You should have a doc look at it.
Atopic dermatitis . Consider using non perfumed soaps and lotions. I would recommend dove soap and either eucerin or aveeno (oatmeal) lotion. I would also recommend a due free detergent and to avoid dryer sheets.