Son has small puncture/hole the size of pencil eraser in back of his throat. Do we seek medical attention?

Yes. Go to the emergency room tonight. There is the potential for a serious infection.
Yes. Although, you may be looking at the space between two lymphoid follicles in the back of the pharynx (throat), you need piece of mind that this is not an ulceration from a virus. See an ENT doctor for a correct diagnosis. Also has he had his tonsils removed? You may be looking at the result of the surgical healing.