My four year old has two swollen hard bumps behind his right ear I'm assuming it's his lymph nodes but I feel two but they don't hurt?

Bumps. The bumps are most likely lymph nodes which is nothing to worry about. It takes a long time to go away .
If they are pea-size. or a little larger, they may be reactive lymph nodes from scalp irritation or even a systemic viral illness. If they grow alarmingly rapidly or if they are are already quite large, have his pediatrician examine him this coming week. They'd still most likely be lymph nodes, but it would be good to look for the cause of their rapid enlargement. .