baby sunburn

please help. my baby boy is 6 months old and we took him to the pool today and I put sunscreen on like usual and he had his hat and everything but this time his gramma was holding him and I didn't realize he was getting burnt until it was too late. now his one arm is very red and burnt. he is acting fine and not in pain(yet) but what do you ladies do when you're babies get burnt? I usually would just use aloe on myself. can I use it on him? what do you guys think??