I see 4 bumps on my sons head could it be chicken pox?

DON'T THINK SO: You didn't mention age, state of chicken pox immunization (if more than 1 year). Chicken pox usually comes on covered areas (centripetal distribution), e.g. Axilla, chest, trunk, but can start anywhere, face, scalp extremities. You can see all 4 stages of rash same time, macules (flat pinkish), papules (raised), vesicles and pustules, when full blown. If coming more, let his ped doc. Have a look.