Pain and discomfort is normal. If the lymph nodes are getting larger or more painful, i would touch base with your nurses because you could have some sort of infection going on. You would want that nipped in the bud.

That said, anything going into your body that is deemed foreign can cause a node reaction because foreign things are treated as invaders. Wednesday is still very recent, and inflammation usually peaks on day 3 or 4 and you can get more discomfort days later than on the day or next day.