My eight year old said he can feel his pulse in the roof of his mouth today? what could this be. no other health issues

Palatine artery: Could be that he feels his palatine artery - which could be a normal thing. If he is well ans just feels once in awhile - nothing to worry about. Your child doctor can examine his palate on your son's next visit

Teething: 8 year old are often in the process of losing their baby teeth and growing in adult teeth, which can cause inflammation of the gums, and feel like a pulsating pain. If it continues, I would consult his dentist or primary doctor just to be sure.