Hello. My 2 Year Old Son Had Been Developing These

Hello. My 2 year old son had been developing these lumps and bumps on his neck area. These lumps are hard and to me seem like muscle knots in a way. I am worried because at first it started with one on one side but now he has 2 on each side. And I would like to know if its possibly a tumor and what and where I can go to get him checked out. Thank you