Hi my son is 8 years old today i saw a big bold spot on his head no hair, his not scratching im worried?

Alopecia: People can lose a spot of hair without having other health issues. Here is a article on the subject: https://www.mayoclinic.org/diseases-conditions/hair-loss/symptoms-causes/syc-20372926

Some basics: Such a bald spot can represent many things from a birth defect, to a past fungal infection, to hair twirling & eating and others. The need for or type of treatments would be sorted out starting with a visit to his doc or as dermatologist.