SSmiles
Yes it is best to clean it when the skin is retracted with soap and water, this enables you wash away anything that has collected under the foreskin.
Rayray
Some children do get upset about getting an erection. I’m not 100% sure why but I believe it to be related to body image. They are used to their penis being soft and flaccid then all of a sudden it becomes hard. They obviously do not know the reason for the change and it can cause them to become concerned. One reason for ‘hiding his penis’ could again be related to body image. He is used to seeing his penis with the foreskin covering the head, when the skin is retracted it looked different and therefore he pulls the foreskin forward to make it look “normal” again. This is only an educated guess and I may be completely wrong but it is something for you to consider.